In vivo ameliorative effects of vitamin E against hydralazine-induced lupus.

OBJECTIVE: In this study, we investigated the in vivo ameliorative effects of vitamin E in a hydralazine-induced lupus model, which closely resembles SLE in humans. We aim to shed light on its potential as a therapeutic agent for managing SLE. METHODS: Forty BALB/c mice were used in this study. Hydralazine hydrochloride was orally administered in a concentration of 25 mg/kg to the five mice groups once weekly for a period of 5 weeks to induce a lupus-like condition. The untreated group was the normal control group. To confirm the development of lupus, an ANA test was conducted. After the mice tested positive for ANA, drug treatments commenced. The negative control group did not receive any drug treatment. The treatments included prednisolone, methotrexate and vitamin E, all administered at a concentration of 25 mg/kg, with a higher dose of vitamin E (50 mg/kg) also administered. RESULTS: Notably, on day 35, after drug treatment, we observed that mice that received vitamin E at a dosage of 50 mg/kg (3.01±0.100) had a slight decrease in lymphocyte hydrogen peroxide radicals when compared with the group receiving 25 mg/kg of vitamin E (3.30±0.100) (p<0.05). This finding suggests that the scavenging potential of vitamin E is dose dependent. CONCLUSION: This study suggests that vitamin E supplementation, especially at a higher dose (50 mg/kg), holds promise in ameliorating lupus-like conditions. These findings warrant further exploration and may offer a potential avenue for improving the disease status of patients experiencing SLE.

Combination Sodium Nitrite and Hydralazine Therapy Attenuates Heart Failure With Preserved Ejection Fraction Severity in a "2-Hit" Murine Model.

Background Recent studies have suggested that cardiac nitrosative stress mediated by pathological overproduction of nitric oxide (NO) via inducible NO synthase (iNOS) contributes to the pathogenesis of heart failure with preserved ejection fraction (HFpEF). Other studies have suggested that endothelial NO synthase (eNOS) dysfunction and attenuated NO bioavailability contribute to HFpEF morbidity and mortality. We sought to further investigate dysregulated NO signaling and to examine the effects of a NO-based dual therapy (sodium nitrite+hydralazine) following the onset of HFpEF using a "2-hit" murine model. Methods and Results Nine-week-old male C57BL/6 N mice (n=15 per group) were treated concurrently with high-fat diet and N(ω)-nitro-L-arginine methyl ester (L-NAME) (0.5 g/L per day) via drinking water for 10 weeks. At week 5, mice were randomized into either vehicle (normal saline) or combination treatment with sodium nitrite (75 mg/L in the drinking water) and hydralazine (2.0 mg/kg IP, BID). Cardiac structure and function were monitored with echocardiography and invasive hemodynamic measurements. Cardiac mitochondrial respiration, aortic vascular function, and exercise performance were also evaluated. Circulating and myocardial nitrite were measured to determine the bioavailability of NO. Circulating markers of oxidative or nitrosative stress as well as systemic inflammation were also determined. Severe HFpEF was evident by significantly elevated E/E', LVEDP, and Tau in mice treated with L-NAME and HFD, which was associated with impaired NO bioavailability, mitochondrial respiration, aortic vascular function, and exercise capacity. Treatment with sodium nitrite and hydralazine restored NO bioavailability, reduced oxidative and nitrosative stress, preserved endothelial function and mitochondrial respiration, limited the fibrotic response, and improved exercise capacity, ultimately attenuating the severity of "two-hit" HFpEF. Conclusions Our data demonstrate that nitrite, a well-established biomarker of NO bioavailability and a physiological source of NO, is significantly reduced in the heart and circulation in the "2-hit" mouse HFpEF model. Furthermore, sodium nitrite+hydralazine combined therapy significantly attenuated the severity of HFpEF in the "2-hit" cardiometabolic HFpEF. These data suggest that supplementing NO-based therapeutics with a potent antioxidant and vasodilator agent may result in synergistic benefits for the treatment of HFpEF.

Race/ethnicity differences in response to acute antihypertensive treatment of peripartum severe hypertension.

BACKGROUND: Hypertensive disorders of pregnancy increase maternal morbidity, mortality, and long-term risk for cardiovascular disease. The rising incidence of chronic hypertension and preeclampsia disproportionately affects people of color. There is a paucity of published data examining differences in the effectiveness of acute antihypertensive agents between pregnant patients of different races/ethnicities. We aimed to determine if the effectiveness of acute antihypertensive agents for peripartum severe hypertension differs by race/ethnicity. METHODS: A retrospective cohort study of patients with severe peripartum hypertension (systolic blood pressure ≥ 160 mmHg and/or diastolic blood pressure ≥ 110 mm Hg confirmed within 15 min) to determine whether the effectiveness of blood pressure control using nationally recommended medications (hydralazine, labetalol, nifedipine) differed by race/ethnicity. The primary outcome was reduction and maintenance of blood pressure to target ranges (140-150/90-100 mm Hg or below) for ≥4 h in each race/ethnicity group. Statistical tests included χ2, Fisher's exact, analysis of variance, and multivariable logistic regression. RESULTS: Of 729 patients receiving treatment for severe peripartum hypertension, all medications were effective (overall 86.4% efficacy) at controlling blood pressure. Labetalol was the most effective medication in White patients (93.0 vs. 74.7% for nifedipine and 86.5% for hydralazine, p < .001). No overall differences in medication effectiveness were found in Black, Asian, or LatinX patients. Black and Asian patients were more likely to experience >1 hypertensive episode [51.0 and 49.0%, respectively vs. 35.4% (White) and 40.0% (LatinX), p = .008]. CONCLUSION: Currently recommended therapies for severe peripartum hypertension are effective in controlling blood pressure for ≥4 h in patients of all race/ethnic groups. Labetalol was the most effective medication in White patients with no overall differences in medication effectiveness in Black, Asian, or LatinX patients.

Different dosage regimens of nifedipine, labetalol, and hydralazine for the treatment of severe hypertension during pregnancy: a network meta-analysis of randomized controlled trials.

OBJECTIVES: This network meta-analysis aimed to compare the efficacy and safety of intravenous (IV) hydralazine, oral nifedipine, and IV labetalol with different dosage regimens in the treatment of severe hypertension during pregnancy. METHODS: A comprehensive literature search was performed on PubMed, Embase, the Cochrane Library, and ClinicalTrials.gov for randomized controlled trials (RCTs) exploring the effects of hydralazine, nifedipine, and labetalol in the treatment of severe hypertension during pregnancy. RESULTS: A total of 21 RCTs with 2183 patients comparing 7 regimens (oral nifedipine 50,60,90 mg; hydralazine 15,25 mg; and labetalol 220,300 mg) were identified. Compared with IV labetalol 300 mg, nifedipine 50,60, and 90 mg significantly improved the successful treatment rate of severe hypertension during pregnancy, nifedipine 50 and 90 mg and IV hydralazine 25 mg required significantly fewer doses to achieve target blood pressure (BP), and nifedipine 50 mg took significantly shorter time to achieve target BP. Subgroup analysis showed that only nifedipine 50 mg tablets, not capsules, required a significantly shorter time and fewer doses to achieve target BP than IV labetalol 300 mg. Moreover, nifedipine 60,90 mg showed superior effectiveness than IV hydralazine 15,25 mg in the successful treatment rate of severe hypertension during pregnancy. SUCRA analysis suggested that nifedipine 50,60,90 mg as the better regimens with the lower rates of overall ADR and neonatal complications. CONCLUSION: These findings demonstrated the superiority of oral nifedipine 50,60,90 mg, especially oral nifedipine 50 mg tablets, in the treatment of severe hypertension during pregnancy than IV labetalol 300 mg, while oral nifedipine 60,90 mg also showed superiority in the successful treatment rate of severe hypertension during pregnancy than IV hydralazine 15,25 mg. However, the limitations of the underlying data indicate that future large-scale and rigorous RCTs are needed to confirm such findings.

Evaluation of Cytochrome P450 Selectivity for Hydralazine as an Aldehyde Oxidase Inhibitor for Reaction Phenotyping.

Hydralazine has been reported as a selective mechanism-based inactivator of aldehyde oxidase (AO) and it is widely used in the pharmaceutical industry for reaction phenotyping to estimate fraction metabolized by AO and to identify AO substrates. In this study, however, hydralazine was found to inhibit CYP1A2, 2B6, 2D6, and 3A in human suspension hepatocytes under reaction phenotyping assay conditions, at concentrations that chemically knocked out most of the AO activities (≥50 µM). Furthermore, hydralazine is a time-dependent inhibitor of CYP1A2. Based on these findings, precautions need to be taken when using hydralazine as an AO inhibitor for in vitro studies because fraction metabolized by AO is likely to be overestimated and the likelihood of false positives in identifying AO substrates increases.

Acrolein Scavenger Hydralazine Prevents Streptozotocin-Induced Painful Diabetic Neuropathy and Spinal Neuroinflammation in Rats.

Diabetes-induced neuropathic pain (DNP) substantially influences people's life qualities. Hyperglycemia-induced excess free radicals have been considered as the most critical mechanisms underlying DNP. As an unsaturated aldehyde and a reactive product of lipid peroxidation, acrolein plays critical roles in diabetic nephropathy and inflammatory pain. We sought to determine whether acrolein is involved in DNP in this study. Diabetes was induced by a single intraperitoneal (i.p.) injection of 60 mg/kg streptozotocin (STZ). An acrolein scavenger hydralazine (5 mg/kg) was administered through a daily injection for 4 weeks, starting immediately within 30 min after STZ injection. Western blot showed that hydralazine could effectively inhibit STZ-induced upregulation of acrolein in the spinal dorsal horn on day 7-28 after STZ injection. Behavioral tests showed that STZ injection induced significant mechanical allodynia and thermal hyperalgesia, which could be alleviated by hydralazine. Immunofluorescent histochemistry and Western blot showed that STZ induced significant microglial activation. ELISA data indicated upregulation of inflammatory cytokines IL-1ß and TNF-α expression in the spinal dorsal horn. Furthermore, hydralazine effectively attenuated microglial activation and expression of inflammatory mediators. Our data indicate that acrolein might be involved in the development of neuroinflammation and behavioral consequences of DNP. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:1858-1864, 2017. © 2017 Wiley Periodicals, Inc.

Therapeutic Effects of Procainamide on Endotoxin-Induced Rhabdomyolysis in Rats.

Overt systemic inflammatory response is a predisposing mechanism for infection-induced skeletal muscle damage and rhabdomyolysis. Aberrant DNA methylation plays a crucial role in the pathophysiology of excessive inflammatory response. The antiarrhythmic drug procainamide is a non-nucleoside inhibitor of DNA methyltransferase 1 (DNMT1) used to alleviate DNA hypermethylation. Therefore, we evaluated the effects of procainamide on the syndromes and complications of rhabdomyolysis rats induced by lipopolysaccharide (LPS). Rhabdomyolysis animal model was established by intravenous infusion of LPS (5 mg/kg) accompanied by procainamide therapy (50 mg/kg). During the experimental period, the changes of hemodynamics, muscle injury index, kidney function, blood gas, blood electrolytes, blood glucose, and plasma interleukin-6 (IL-6) levels were examined. Kidneys and lungs were exercised to analyze superoxide production, neutrophil infiltration, and DNMTs expression. The rats in this model showed similar clinical syndromes and complications of rhabdomyolysis including high levels of plasma creatine kinase, acute kidney injury, hyperkalemia, hypocalcemia, metabolic acidosis, hypotension, tachycardia, and hypoglycemia. The increases of lung DNMT1 expression and plasma IL-6 concentration were also observed in rhabdomyolysis animals induced by LPS. Treatment with procainamide not only inhibited the overexpression of DNMT1 but also diminished the overproduction of IL-6 in rhabdomyolysis rats. In addition, procainamide improved muscle damage, renal dysfunction, electrolytes disturbance, metabolic acidosis, hypotension, and hypoglycemia in the rats with rhabdomyolysis. Moreover, another DNMT inhibitor hydralazine mitigated hypoglycemia, muscle damage, and renal dysfunction in rhabdomyolysis rats. These findings reveal that therapeutic effects of procainamide could be based on the suppression of DNMT1 and pro-inflammatory cytokine in endotoxin-induced rhabdomyolysis.

Pentosan polysulfate preserves renal microvascular P2X1 receptor reactivity and autoregulatory behavior in DOCA-salt hypertensive rats.

Inflammation contributes to ANG II-associated impairment of renal autoregulation and microvascular P2X1 receptor signaling, but its role in renal autoregulation in mineralocorticoid-induced hypertension is unknown. Autoregulatory behavior was assessed using the blood-perfused juxtamedullary nephron preparation. Hypertension was induced in uninephrectomized control rats (UNx) by subcutaneous implantation of a DOCA pellet plus administration of 1% NaCl in the drinking water (DOCA-salt) for 3 wk. DOCA-salt rats developed hypertension that was unaltered by anti-inflammatory treatment with pentosan polysulfate (DOCA-salt+PPS) but was suppressed with "triple therapy" (hydrochlorothiazide, hydralazine, and reserpine; DOCA-salt+TTx). Baseline arteriolar diameters were similar across all groups. UNx rats exhibited pressure-dependent vasoconstriction with diameters declining to 69 ± 2% of control at 170 mmHg, indicating intact autoregulation. DOCA-salt treatment significantly blunted this pressure-mediated vasoconstriction. Diameters remained between 91 ± 4 and 98 ± 3% of control over 65-170 mmHg, indicating impaired autoregulation. In contrast, pressure-mediated vasoconstriction was preserved in DOCA-salt+PPS and DOCA-salt+TTx rats, reaching 77 ± 7 and 75 ± 3% of control at 170 mmHg, respectively. ATP is required for autoregulation via P2X1 receptor activation. ATP- and ß,γ-methylene ATP (P2X1 receptor agonist)-mediated vasoconstriction were markedly attenuated in DOCA-salt rats compared with UNx (P < 0.05), but significantly improved by PPS or TTx (P < 0.05 vs. DOCA-salt) treatment. Arteriolar responses to adenosine and UTP (P2Y2 receptor agonist) were unaffected by DOCA-salt treatment. PPS and TTx significantly reduced MCP-1 and protein excretion in DOCA-salt rats. These results support the hypothesis that hypertension triggers inflammatory cascades but anti-inflammatory treatment preserves renal autoregulation in DOCA-salt rats, most likely by normalizing renal microvascular reactivity to P2X1 receptor activation.

Evaluation of cardiovascular changes in dogs administered three positive controls using jacketed external telemetry-blood pressure (JET-BP).

INTRODUCTION: Nonclinical safety studies are increasingly incorporating cardiac safety endpoints to discover potential cardiovascular liabilities. This trend for more thorough cardiovascular nonclinical safety evaluation is prudent given the high attrition rate of potential therapeutics due to unexpected cardiovascular liabilities discovered in late-stage clinical trials or post-market approval. In particular, the causal relationship of blood pressure changes that lead to risk of major adverse cardiac events suggests hemodynamic changes should be critically evaluated in preclinical studies of novel therapeutics. METHODS: Jacketed external telemetry with an implanted miniature blood pressure transmitter (JET-BP) was used to characterize the tolerability, functionality, and sensitivity of this study design in dogs. Thirty-six male or female beagles (n=6 dogs/sex/group) were administered vehicle control (reverse osmosis water) or etilefrine (1, 10mg/kg), sotalol (3, 30mg/kg), and hydralazine (1, 10mg/kg) on separate days. Telemetry data were evaluated for positive control article-related changes and retrospective power analysis was also completed. Animals were evaluated for instrumentation-related changes in clinical and anatomic pathology endpoints. RESULTS: All three positive controls elicited the expected pharmacologic responses that were statistically different at high and low doses. Retrospective power analysis confirmed this study design was able to statistically differentiate minor (approximately 5 to 15%) changes in electrocardiography and blood pressure values. This study also demonstrated the potential advantages of combining cardiovascular data across sex when the test article exposure and pharmacodynamics were consistent. Data collection using miniature telemetry blood pressure transmitters did not result in anatomic or clinical pathology findings that would prevent their use in general toxicology studies. DISCUSSION: This characterization study indicates that JET-BP in dogs offers a scientifically-robust method to evaluate novel therapeutics for potential cardiovascular liabilities.

Characterization of aldehyde oxidase enzyme activity in cryopreserved human hepatocytes.

Substrates of aldehyde oxidase (AO), for which human clinical pharmacokinetics are reported, were selected and evaluated in pooled mixed-gender cryopreserved human hepatocytes in an effort to quantitatively characterize AO activity. Estimated hepatic clearance (Cl(h)) for BIBX1382, carbazeran, O6-benzylguanine, zaleplon, and XK-469 using cryopreserved hepatocytes was 18, 17, 12, <4.3, and <4.3 ml · min⁻¹ · kg⁻¹, respectively. The observed metabolic clearance in cryopreserved hepatocytes was confirmed to be a result of AO-mediated metabolism via two approaches. Metabolite identification after incubations in the presence of H2¹8O confirmed that the predominant oxidative metabolite was generated by AO, as expected isotope patterns in mass spectra were observed after analysis by high-resolution mass spectrometry. Second, clearance values were efficiently attenuated upon coincubation with hydralazine, an inhibitor of AO. The low exposure after oral doses of BIBX1382 and carbazeran (∼5% F) would have been fairly well predicted using simple hepatic extraction (f(h)) values derived from cryopreserved hepatocytes. In addition, the estimated hepatic clearance value for O6-benzylguanine was within ∼80% of the observed total clearance in humans after intravenous administration (15 ml · min⁻¹ · kg⁻¹), indicating a reasonable level of quantitative activity from this in vitro system. However, a 3.5-fold underprediction of total clearance was observed for zaleplon, despite the 5-oxo metabolite being clearly observed. These data taken together suggest that the use of cryopreserved hepatocytes may be a practical approach for assessing AO-mediated metabolism in discovery and potentially useful for predicting hepatic clearance of AO substrates.

"Pulse" treatment with high-dose angiotensin blocker reverses renal arteriolar hypertrophy and regresses hypertension.

One ultimate goal of hypertension therapy is to cause permanent reversal ("regression") of already established hypertension. Our aim was to examine whether high-dose "pulse" treatment with a renin-angiotensin system inhibitor could cause regression of established hypertension and to link this action to reversal of arteriolar hypertrophy and changes in vascular matrix metalloproteinase activities. First, 16-week-old male spontaneously hypertensive rats (n=60) were pulse treated for 2 weeks with high-dose angiotensin-converting enzyme inhibitor (enalapril), angiotensin receptor blocker (candesartan), calcium channel blocker (nifedipine), or vasodilator (hydralazine) with or without salt restriction, and the long-term effects on blood pressure were examined. Second, spontaneously hypertensive rats were treated with angiotensin receptor blocker or calcium channel blocker, and the effects on renal gene expressions, arteriolar structure, and vascular matrix metalloproteinase were compared. Treatment of spontaneously hypertensive rats with different antihypertensive agents caused apparently similar reductions in blood pressure during the course of the pulse treatment, within the limitations of the tail-cuff method. After cessation of medications, blood pressure in the rats treated with renin-angiotensin system inhibitor remained reduced by >30 to 40 mm Hg for 4 months. No such effect was seen with calcium channel blocker or vasodilator. The 2-week angiotensin receptor blocker treatment induced a marked reversal of the arteriolar hypertrophy specifically in the small (30 to 100 microm) renal arterioles, together with increased expression and activity of matrix metalloproteinase-13. In conclusion, transient high-dose pulse treatment with angiotensin receptor blocker caused changes in vascular matrix metalloproteinase activity, specific reversal of renal arteriolar hypertrophy, and regression of hypertension in spontaneously hypertensive rats.

Pharmacologically induced angiogenesis in transgenic zebrafish.

The rapid vascularisation of biomaterials and engineered tissue after implantation is a current unmet need. To this end, we explored the pharmacological option of inducing neovascularisation using compounds that inhibit hypoxia-induced factor-1alpha prolyl hydroxylase. This stabilises hypoxia inducible factor-1alpha and therefore de-repress the transcription of various angiogenic genes. In the quest for a small vertebrate model allowing for in vivo screening we exposed (TG(Fli1:EGFP)) transgenic zebrafish embryos exhibiting fluorescent blood vessels to hydralazine hydrochloride and 2,4-pyridine dicarboxylic acid from 6hpf to 72hpf by immersion. Live observation of embryos revealed that the substances induced formation of ectopic blood vessels in the subintestinal vessel basket. We confirmed the HIF-stabilising effects biochemically in human fibroblasts and with an in vitro angiogenesis fibroblast/HUVEC co-culture model. Cross-inhibition of collagen prolyl hydroxylase was confirmed by reduced collagen secretion by fibroblasts and reduced collagen content of zebrafish embryos.

Hyperbaric oxygenation reduces overexpression of c-Fos and oxidative stress in the brain stem of experimental endotoxemic rats.

OBJECTIVE: Septic encephalopathy is associated with an increased mortality rate in septic patients. We have previously shown that a peripheral lipopolysaccharide (LPS) injection induces neuronal activation in the brain-stem nuclei of rats. Nitric oxide (NO) and superoxide are involved in LPS-induced brain damage. Hyperbaric oxygenation (HBO) provides protective effects against systemic oxidative stress and mortality in animals with septic shock. We examined the effects of HBO on neuronal activation and oxidative stress in the brain-stem nuclei of LPS-treated rats. DESIGN AND INTERVENTIONS: Wistar rats were randomly distributed into six groups for the following treatments:(a) normal saline injection (NS); (b) HBO; (c) LPS; (d) LPS-HBO; (e) LPS-aminoguanidine (AG, an inhibitor of inducible nitric oxide synthase); or (f) hydralazine (HYD, a direct vasodilator). The HYD induces prolonged hypotension and was used as a comparison for LPS stimulation. The AG was used as a comparison for HBO treatment. Two HBO sessions were administered, 1 and 4[Symbol: see text]h after LPS. RESULTS: HBO and AG significantly reversed the overproduction of c-Fos induced by LPS in the brain stems of rats, with greater reversal in the nucleus tractus solitarii (NTS) by HBO. Although AG did not reduce the superoxide level, HBO significantly abolished superoxide production and NADPH diaphorase expression in the brain stems of LPS-treated rats. The HYD induced much lower c-Fos expression in the brain-stem nuclei than that in LPS-treated animals and caused no significant increase in NADPH diaphorase expression or superoxide formation. CONCLUSION: HBO protects against endotoxin-related neuronal activation and oxidative stress in the brain-stem nuclei of rats.

Tachykinin NK3 receptor contribution to systemic release of vasopressin and oxytocin in response to osmotic and hypotensive challenge.

Activation of the neurokinin 3 receptor (NK3R) by a receptor agonist, hypotension, and hyperosmolarity results in the internalization of NK3R expressed by magnocellular neurons and the release of vasopressin (VP) and oxytocin (OT) into the circulation. The contribution of NK3R activation to the release of VP and OT in response to hyperosmolarity and hypotension was evaluated by measuring the release of both hormones following pretreatment with a selective NK3R antagonist, SB-222200. Freely behaving male rats were given an intraventricular injection of either 0.15 M NaCl or 250, 500, or 1,000 pmol SB-222200, and then were administered an intravenous infusion of 2 M NaCl or 0.15 M NaCl (experiment 1), or a bolus intra injection of 0.15 M NaCl or hydralazine (HDZ), a hypotension-inducing drug (experiment 2). Blood samples were taken from indwelling arterial catheters at various time points for 1-2 h, both before and after treatments. Plasma VP and OT levels were determined by ELISA. Blockade of NK3R did not affect the baseline levels of either hormone. In contrast, pretreatment with SB-222200 significantly reduced ( approximately 60%) or abolished the release of VP and OT, respectively, to 2 M NaCl infusion. HDZ-induced VP and OT release was eliminated by pretreatment with 500 pmol SB-222200. Therefore, NK3R activation contributes significantly to the systemic release of both VP and OT in response to osmotic and hypotensive challenges.

Impact of antihypertensive treatments on erectile responses in aging spontaneously hypertensive rats.

OBJECTIVE: We previously demonstrated that brief, aggressive antihypertensive therapy recovered erectile function in 40-week-old spontaneously hypertensive rats (SHR). The present study examined the impact of antihypertensive and testosterone treatments on erectile function in aging SHR. DESIGN AND METHODS: Centrally initiated erections were determined in response to apomorphine throughout. At 30 and 49 weeks, SHR were treated for 2 weeks with enalapril or hydralazine. A third more aggressive treatment (68 weeks) involved enalapril or losartan plus a low salt diet or a triple therapy (hydralazine, nifedipine, hydrochlorothiazide). In a separate study, cross-over kidney transplantations were performed between untreated and losartan-treated SHR. Arterial pressure was assessed post-transplantation using radio-telemetric transducers. RESULTS: There was an age-related decrease in erections between 30 and 68 weeks (3.1 +/- 0.79 versus 0.2 +/- 0.38) that was not improved by testosterone administration. Early treatment with enalapril or hydralazine did not prevent this decline, although the second treatment resulted in significant improvements (enalapril, 0.8 +/- 0.70; hydralazine, 0.8 +/- 0.41 versus control, 0.3 +/- 0.60). A 2-week aggressive antihypertensive treatment at 68 weeks increased erections approximately two-fold, with the previously treated rats receiving triple therapy having markedly improved erectile responses (0.2 +/- 0.53 versus 1.1 +/- 1.67). In the transplantation study, previously losartan-treated SHR given an untreated kidney had higher arterial pressure but twice the number of erections in comparison with the SHR with lower arterial pressure resulting from transplanting a treated kidney. CONCLUSIONS: Aggressive antihypertensive treatments may be more beneficial in improving erectile function in aged SHR, via an effect that appears to be tissue specific, and not based on changes in blood pressure.

Anti-hypertensive therapy and the feto-placental circulation: effects on umbilical artery resistance.

OBJECTIVE: To investigate and compare the direct effects of compounds used in the treatment of hypertensive disease in pregnancy on human umbilical artery resistance in vitro. METHODS: Isometric tension recordings were performed under physiological conditions on human umbilical arterial rings (n=30). The in vitro effects of labetolol, hydralazine, alpha-methyldopa, nifedepine and magnesium sulphate (at concentration ranges from 1 nanomolar to 1 millimolar), and their respective vehicle controls, were measured. Results were expressed as -logEC50 (pD2) and mean maximal inhibition values for each compound. RESULTS: All compounds investigated, except alpha methyldopa, exerted a significant relaxant effect on umbilical arterial tone. Alpha-methyldopa was significantly less potent when compared to all other compounds (mean maximal inhibition value [20.89+/-7.99%] versus all other agents [range 63.15+/-8.70-84.12+/-3.84%] (P<0.01)). The dose response curve of nifedipine yielded a significantly greater PD2 value when compared to that of hydralazine, labetalol, and magnesium sulphate (PD2 value [5.82+/-0.34] versus the above groups [range 3.10+/-0.09-3.52+/-0.14] (P <0.01)). CONCLUSION: These findings demonstrate that agents commonly used for the treatment of hypertensive disease in pregnancy, excluding alpha-methyldopa, have significant direct effects on the feto-placental circulation. These results suggest that alpha-methyldopa administration during pregnancy is less likely to produce significant direct effects on fetal vasculature then other agents used.

Persistent lowering of arterial pressure after continuous and intermittent therapy.

OBJECTIVE: The present study investigates the impact of antihypertensive treatment on persistent reduction of arterial pressure after cessation of drug treatment. DESIGN AND METHODS: Specifically, adult spontaneously hypertensive rats (SHR) were treated for 6 weeks with inhibitors of the renin-angiotensin system (RAS), or combination therapy (hydralazine, nifedipine, hydrochlorothiazide) and following a 14-week 'drug holiday', were re-treated for 4 weeks. Mean arterial pressure (MAP) was continuously monitored via radiotelemetry. RESULTS: Comparison in the first off-treatment period revealed that RAS inhibitor drugs produced a 16-18% persistent lowering of arterial pressure, whereas the triple therapy induced a 10% lowering of MAP relative to untreated SHR. The drug re-challenge induced a further 9% reduction in the 'off'-treatment level of MAP such that in all treatment groups MAP was reduced by more than 30 mmHg compared with controls. CONCLUSIONS: This study provides new evidence that combination therapy, not directly targeting the RAS, can be efficacious in persistently reducing MAP off-treatment. Furthermore, we demonstrated that the 6-week treatment with RAS inhibitors induced equivalent persistent changes as a 10-week treatment. That is, the additional 4 weeks of continuous therapy was ineffective in further altering the off-treatment MAP. In contrast, with the intermittent treatment protocol (the 14-week 'drug holiday') a further effect on persistent lowering of MAP was regained. These findings suggest continuous long-term treatment with antihypertensive drugs may not be the most effective means of reversing underlying circulatory abnormalities and that the introduction of a drug holiday may be beneficial.

Neuroprotective effect of treatment with calcium antagonists on hypertensive retina.

The influence of hypertension and of treatment with the dihydropyridine-type Ca2+ antagonists lercanidipine, manidipine, nicardipine, and nimodipine and with non dihydropyridine-type vasodilator hydralazine on retinal nervous and glial fibrillary acidic protein (GFAP) immunoreactive astrocytes were investigated in male spontaneously hypertensive rats (SHR). Normotensive Wistar-Kyoto (WKY) were used as normotensive references group. Treatment of animals with oral equi-hypotensive doses of the above compounds started at 14 weeks of age and lasted for 12 weeks. Microanatomical analysis was extended to samples of frontal cortex and occipital cortex used as reference tissue. Different compounds investigated decreased to a similar extent systolic blood pressure values with the exception of nimodipine that in spite of the high dose used exerted a less pronounced hypotensive activity. Morphological changes including reduced thickness of retina and of inner plexiform, outer nuclear and layer of inner and outer segments plus outer limiting layer, and loss of ganglionic neurons were observed. GFAP-immunoreactive astrocyte hypertrophy was also found in control SHR. These phenomena were countered by treatment by treatment with dihydropyridine-type Ca2+ antagonists and to a lesser extent by hydralazine. The different Ca2+ antagonists tested exerted a similar protective effect on retinal, but not on brain neurons. The sensitivity of retina and cerebral cortex to anti-hypertensive treatment may be related to a different density of L-type Ca2+ channels in structures investigated or to kinetic reasons. The demonstration of a neuroprotective effect of Ca2+ antagonists on retina of SHR suggests that these compounds might protect to a some extent retina from hypertensive injury.

Impact of hydroxymethylglutaryl coenzyme a reductase inhibition on left ventricular remodeling after myocardial infarction: an experimental serial cardiac magnetic resonance imaging study.

OBJECTIVES: We sought to assess the influence of long-term hydroxymethylglutaryl coenzyme A reductase inhibition (statin) therapy on left ventricular (LV) remodeling after myocardial infarction (MI) by use of serial cardiac magnetic resonance imaging (CMRI) studies. BACKGROUND: Statin therapy has been shown to reduce cardiac hypertrophy in vitro and in vivo, but the influence on LV post-MI remodeling is largely unknown. METHODS: The CMRI measurements were taken four and 12 weeks after left coronary artery ligation in a 7.05-tesla Biospec. The MI size, LV mass and volumes, cardiac output (CO), and ejection fraction were determined. Rats were treated for 12 weeks with either placebo (P), cerivastatin (C; 0.6 mg/kg body weight per day) as a dietary supplement, or cerivastatin plus the nitric oxide synthase (NOS) inhibitor N-methyl-L-arginine methyl ester (L-NAME, 76 mg/100 ml) and hydralazine (8 mg/100 ml) in drinking water (CLH) to assess the contribution of endogenous nitric oxide formation. RESULTS: Administration of cerivastatin attenuated hypertrophy after MI, and this effect was completely abolished by NOS inhibition (increase of LV mass from 4 to 12 weeks after MI: 235.3 +/- 33.7 mg with P vs. 59.8 +/- 20.5 mg with C vs. 239.5 +/- 16.0 mg with CLH; p < 0.05 vs. P and CLH). Left ventricular dilation was not changed (increase of end-diastolic volume from 4 to 12 weeks after MI: 108.7 +/- 28.8 with P vs. 126.6 +/- 20.5 with C vs. 173.7 +/- 25.1 with CLH; p = NS). The CO was higher in the cerivastatin group (12 weeks: 76.1 +/- 2.9 ml/min with P vs. 95.8 +/- 4.8 ml/min with C; p < 0.05). The effects of cerivastatin were abolished by NOS inhibition in the CLH group (CO at 12 weeks: 69.3 +/- 2.8 ml/min, p < 0.05 vs. C). CONCLUSIONS: Left ventricular remodeling was profoundly changed by statin treatment. Hypertrophy was attenuated, and global function was improved. These positive effects were abolished by NOS inhibition.

Occurrence and distribution of atrial natriuretic peptide-containing cells in the left ventricle of hypertensive rats. Effect of antihypertensive treatment.

In the ventricles of adult mammalian hearts, production of atrial natriuretic peptide (ANP) is negligible, restricted to the impulse-conducting cells, the papillary muscles, and a minority of subendocardial myocytes. ANP expression is reinduced in the ventricles of pressure-overloaded and failing hearts and is frequently used as a marker for myocyte hypertrophy. Using an immunohistochemical approach, we have characterized the size distribution of ANP-containing myocytes in the left ventricle of the spontaneously hypertensive rat (SHR) before and after chronic antihypertensive therapy and compared the results to age-matched normotensive Wistar rats (WR). Our findings show that in SHR the frequency of cells presenting ANP granularity is positively correlated with myocyte size (r=0.746, P<0.02). The highest proportion of ANP-positive myocytes (55-57%) was measured among cells of diameters 30-34 microm. In any corresponding cell size, the proportion of ANP-presenting myocytes was five- to tenfold higher in SHR than in the normotensive WR. We studied the effects of the antihypertensive drugs captopril, hydralazine, and nifedipine and found that, regardless of their effect on blood pressure or hypertrophy, all three eliminated ANP immunoproducts from the majority of the left ventricular myocytes and reduced the level of ANP mRNA, captopril being the most effective. The positive correlation between myocyte size and ANP expression was not maintained in the hearts of drug-treated SHR. Myocytes on the border of fibrotic areas or in regions of ANP presentation within the normal heart resisted the suppressive effect of the antihypertensive therapy, indicating that blood pressure or hypertrophy are not the sole correlates for ANP expression.