Biological effects of the antihypertensive losartan under different ocean acidification scenarios.

Since the last decade, several studies have reported the presence and effects of pharmaceutical residues in the marine environment, especially those of the antihypertensive class, such as losartan. However, there is little knowledge about the physiological effects of losartan in marine invertebrates regarding its behavior under possible coastal ocean acidification scenarios. The objective of this study was to evaluate biological effects on marine organisms at different levels of the biological organization caused by the compound losartan in water and sediment under coastal ocean acidification scenarios. Water and sediment samples were collected at five sites around the Santos Submarine Sewage outfall (SSO) and two sites around the Guarujá Submarine Sewage Outfall (GSO). Losartan was found in concentrations ranging from

Ecotoxicity of losartan potassium in aquatic organisms of different trophic levels.

The intensive use of the antihypertensive losartan potassium (LOS) has culminated in its high occurrence in aquatic environments. However, insufficient studies had investigated its effects in non-target organisms. In this study, ecotoxicity of LOS was assessed in aquatic organisms from distinct trophic levels (Desmodesmus subspicatus, Daphnia magna, and Astyanax altiparanae). Genotoxicity was assessed by the comet assay in D. magna and A. altiparanae, and biochemical biomarkers for the fish. LOS was more toxic to D. subspicatus (EC50(72h) = 27.93 mg L-1) than D. magna (EC50 = 303.69 mg L-1). Subsequently, this drug showed to induce more DNA damage in D. magna than A. altiparanae, when exposed to 2.5 mg L-1. No significant stress responses were observed by the fish biomarkers, suggesting that higher trophic levels organisms are more tolerant to LOS toxicity. LOS showed relatively low toxic potential for a short period of exposure, but with different patterns of toxicity for the organisms from distinct trophic levels, contributing to further risk assessment of LOS.

Inhibition of Angiotensin Converting Enzyme Impairs Anti-staphylococcal Immune Function in a Preclinical Model of Implant Infection.

Background: Evidence suggests the renin-angiotensin system (RAS) plays key immunomodulatory roles. In particular, angiotensin-converting enzyme (ACE) has been shown to play a role in antimicrobial host defense. ACE inhibitors (ACEi) and angiotensin receptor blockers (ARB) are some of the most commonly prescribed medications, especially in patients undergoing invasive surgery. Thus, the current study assessed the immunomodulatory effect of RAS-modulation in a preclinical model of implant infection. Methods:In vitro antimicrobial effects of ACEi and ARBs were first assessed. C57BL/6J mice subsequently received either an ACEi (lisinopril; 16 mg/kg/day), an ARB (losartan; 30 mg/kg/day), or no treatment. Conditioned mice blood was then utilized to quantify respiratory burst function as well as Staphylococcus aureus Xen36 burden ex vivo in each treatment group. S. aureus infectious burden for each treatment group was then assessed in vivo using a validated mouse model of implant infection. Real-time quantitation of infectious burden via bioluminescent imaging over the course of 28 days post-procedure was assessed. Host response via monocyte and neutrophil infiltration within paraspinal and spleen tissue was quantified by immunohistochemistry for F4/80 and myeloperoxidase, respectively. Results: Blood from mice treated with an ACEi demonstrated a decreased ability to eradicate bacteria when mixed with Xen36 as significantly higher levels of colony forming units (CFU) and biofilm formation was appreciated ex vivo (p < 0.05). Mice treated with an ACEi showed a higher infection burden in vivo at all times (p < 0.05) and significantly higher CFUs of bacteria on both implant and paraspinal tissue at the time of sacrifice (p < 0.05 for each comparison). There was also significantly decreased infiltration and respiratory burst function of immune effector cells in the ACEi group (p < 0.05). Conclusion: ACEi, but not ARB, treatment resulted in increased S. aureus burden and impaired immune response in a preclinical model of implant infection. These results suggest that perioperative ACEi use may represent a previously unappreciated risk factor for surgical site infection. Given the relative interchangeability of ACEi and ARB from a cardiovascular standpoint, this risk factor may be modifiable.

Depletion of collagen by losartan to improve tumor accumulation and therapeutic efficacy of photodynamic nanoplatforms.

Nanocarriers for drug delivery have made great progress in the treatment of cancer, but the dense extracellular collagen of tumors has greatly limited the efficiency of drug delivery. In this study, losartan is used to deplete tumor collagen and improve the delivery efficiency and photodynamic therapeutic efficacy of chlorine 6 (Ce6)-loaded periodic mesoporous organosilica nanoplatform (Ce6-PMO) for breast cancer. After pretreatment with losartan in vivo, the tumor collagen I fraction is significantly reduced by 53% compared to that of mice pretreated with saline. Importantly, the accumulation of the Ce6-PMO nanoplatforms in the tumor is remarkably enhanced via peritumoral and intravenous injection, respectively, after the mice are pretreated with losartan. Further, combination of losartan with the Ce6-PMO nanoplatforms shows the best therapeutic efficacy, and the suppression rate of tumor volume is measured up to 82%. Taken together, this study provides a very promising synergetic strategy to improve the tumor photodynamic treatment efficacy of nanoplatforms.

Spectroscopic and cytotoxic studies of losartan complexes.

Use of drug-metal complexes for the treatment of several human diseases has resulted in significant progress in the field of medicinal inorganic chemistry. The current study describes the synthesis and characterization of Cu (II) and Ni (II) complexes of Losartan, an antihypertensive drug. These complexes were evaluated for their cytotoxic activity against four human cancer cell lines; SNB-19, HCT-15, COLO-205 and KB-3-1. Spectroscopic characterization revealed that during complex formation, the metal was bound through the nitrogen atoms of the tetrazole moiety of the losartan molecule. The molecular formulas of copper ([Cu (LS) 2 Cl2].6H2O) and nickel ([Ni (LS) 2Cl2]. H2O) complexes were found to be in agreement with the analytical data obtained through elemental analysis. For both the complexes, metal to ligand ratios of 1:2 were calculated. As revealed by FTIR, UV-Visible, and 1H-NMR studies, both the complexes displayed octahedral geometries. Scanning electron microscopy (SEM) revealed marked changes in the morphology of the complexes, compared to the pure drug. From XRD studies, characteristic crystalline peaks of pure losartan were observed whereas no prominent peaks were observed for its complexes. Complexes were found to be inactive in the cytotoxic activity test performed using SNB-19, HCT-15, COLO-205 and KB-3-1 cell lines.

Angiotensin receptor blockade in juvenile male rat offspring: Implications for long-term cardio-renal health.

Inhibition of the renin-angiotensin system in early postnatal life is a potential therapeutic approach to prevent long-term cardiovascular and kidney diseases in individuals born small. We determined the long-term effects of juvenile losartan treatment on cardiovascular and kidney function in control male rat offspring and those exposed to uteroplacental insufficiency and born small. Bilateral uterine vessel ligation (Restricted) or sham (Control) surgery was performed in late gestation in Wistar Kyoto rats. At weaning, male offspring were randomly assigned to receive losartan in their drinking water or drinking water alone from 5 to 8 weeks of age, and followed to 26 weeks of age. Systolic blood pressure and kidney function were assessed throughout the study. Pressure myography was used to assess passive mechanical wall properties in mesenteric and femoral arteries from 26-week-old offspring. Losartan treatment for three weeks lowered systolic blood pressure in both Control and Restricted groups but this difference was not sustained after the cessation of treatment. Losartan, irrespective of birth weight, mildly increased renal tubulointerstitial fibrosis when assessed at 26 weeks of age. Mesenteric artery stiffness was increased by the early losartan treatment, and was associated with increased collagen and decreased elastin content. Losartan also exerted long-term increases in fat mass and decreases in skeletal muscle mass. In this study, untreated Restricted offspring did not develop hypertension, vascular dysfunction or kidney changes as anticipated. Regardless, we demonstrate that short-term losartan treatment in the juvenile period negatively affects postnatal growth, and kidney and vascular parameters in adulthood, irrespective of birth weight. The long-term effects of early-life losartan treatment warrant further consideration in settings where the potential benefits may outweigh the risks; i.e. when programmed adulthood diseases are apparent and in childhood cardiovascular and kidney diseases.

Ecotoxicological effects of losartan on the brown mussel Perna perna and its occurrence in seawater from Santos Bay (Brazil).

The antihypertensive losartan (LOS) has been detected in wastewater and environmental matrices, however further studies focused on assessing the ecotoxicological effects on aquatic ecosystems are necessary. Considering the intensive use of this pharmaceutical and its discharges into coastal zones, our study aimed to determine the environmental concentrations of LOS in seawater, as well as to assess the biological effects of LOS on the marine bivalve Perna perna. For this purpose, fertilization rate and embryolarval development were evaluated through standardized assays. Phase I (ethoxyresorufin O­deethylase EROD and dibenzylfluorescein dealkylase DBF) and II (glutathione S-transferase GST) enzymes, glutathione peroxidase (GPx), Cholinesterase (ChE), lipoperoxidation (LPO) and DNA damage were used to analyze sublethal responses in gills and digestive gland of adult individuals. Lysosomal membrane stability was also assessed in hemocytes. Our results showed the occurrence of LOS in 100% of the analyzed water samples located in Santos Bay, Sao Paulo, Brazil, in a range of 0.2 ng/L-8.7 ng/L. Effects on reproductive endpoints were observed after short-term exposure to concentrations up to 75 mg/L. Biomarker responses demonstrated the induction of CYP450 like activity and GST in mussel gills exposed to 300 and 3000 ng/L of LOS, respectively. GPx activity was also increased in concentration of exposure to 3000 ng/L of LOS. Cyto-genotoxic effects were found in gills and hemocytes exposed in concentrations up to 300 ng/L. These results highlighted the concern of introducing this class of contaminants into marine environments, and pointed out the need to include antihypertensive compounds in environmental monitoring programs.

Evaluation of Trace Elements in Augmentation of Statin-Induced Cytotoxicity in Uremic Serum-Exposed Human Rhabdomyosarcoma Cells.

Patients with end-stage kidney disease (ESKD) are at higher risk for rhabdomyolysis induced by statin than patients with normal kidney function. Previously, we showed that this increase in the severity of statin-induced rhabdomyolysis was partly due to uremic toxins. However, changes in the quantity of various trace elements in ESKD patients likely contribute as well. The purpose of this study is to determine the effect of trace elements on statin-induced toxicity in rhabdomyosarcoma cells exposed to uremic serum (US cells) for a long time. Cell viability, apoptosis, mRNA expression, and intracellular trace elements were assessed by viability assays, flow cytometry, real-time RT-PCR, and ICP-MS, respectively. US cells exhibited greater simvastatin-induced cytotoxicity than cells long-time exposed with normal serum (NS cells) (non-overlapping 95% confidence intervals). Intracellular levels of Mg, Mn, Cu, and Zn were significantly less in US cells compared to that in NS cells (p < 0.05 or 0.01). Pre-treatment with TPEN increased simvastatin-induced cytotoxicity and eliminated the distinction between both cells of simvastatin-induced cytotoxicity. These results suggest that Zn deficiencies may be involved in the increased risk for muscle complaints in ESKD patients. In conclusion, the increased severity of statin-induced rhabdomyolysis in ESKD patients may be partly due to trace elements deficiencies.

Effect of Combined Treatment with AT1 Receptor Antagonists and Tiagabine on Seizures, Memory and Motor Coordination in Mice.

BACKGROUND: Losartan and telmisartan, angiotensin AT1 receptor antagonists, are widely used antihypertensive drugs in patients. It is also known that arterial hypertension is often present in people with epilepsy, therefore, drug interactions between AT1 receptor antagonists and antiepileptic drugs can occur in clinical practice. OBJECTIVES: The aim of the current study was to assess the effect of losartan and telmisartan on the anticonvulsant activity of tiagabine, a second-generation antiepileptic drug, in mice. Additionally, the effect of the combined treatment with AT1 receptor antagonists and TGB on long-term memory and motor coordination has been assessed in animals. MATERIAL AND METHODS: The study was performed on male Swiss mice. Convulsions were examined in the maximal electroshock seizure threshold test. Long-term memory was measured in the passive-avoidance task and motor coordination was evaluated in the chimney test. AT1 receptor antagonists and TGB were administered intraperitoneally. RESULTS: Losartan (50 mg/kg) or telmisartan (30 mg/kg) did not influence the anticonvulsant activity of TGB applied at doses of 2, 4 and 6 mg/kg. However, both AT1 receptor antagonists in combinations with TGB (6 mg/kg) impaired motor coordination in the chimney test. The concomitant treatment of the drugs did not decrease retention in the passive avoidance task. CONCLUSIONS: It is suggested that losartan and telmisartan should not affect the anticonvulsant action of TGB in people with epilepsy. Because the combined treatment with AT1 receptor antagonists and TGB led to neurotoxic effects in animals, caution is advised during concomitant use of these drugs in patients.

Ecotoxicological evaluation of propranolol hydrochloride and losartan potassium to Lemna minor L. (1753) individually and in binary mixtures.

Antihypertensive pharmaceuticals, including the beta-blockers, are one of the most detected therapeutic classes in the environment. The ecotoxicity of propranolol hydrochloride and losartan potassium was evaluated, both individually and combined in a binary mixture, by using the Lemna minor growth inhibition test. The endpoints evaluated in the single-pharmaceutical tests were frond number, total frond area and fresh weight. For the evaluation of the mixture toxicity, the selected endpoint was frond number. Water quality criteria values (WQC) were derived for the protection of freshwater and saltwater pelagic communities regarding the effects induced by propranolol and losartan using ecotoxicological data from the literature, including our data. The risks associated with both pharmaceutical effects on non-target organisms were quantified through the measured environmental concentration (MEC)/predicted-no-effect concentration (PNEC) ratios. For propranolol, the total frond area was the most sensitive endpoint (EC50 = 77.3 mg L(-1)), while for losartan there was no statistically significant difference between the endpoints. Losartan is only slightly more toxic than propranolol. Both concentration addition and independent action models overestimated the mixture toxicity of the pharmaceuticals at all the effect concentration levels evaluated. The joint action of both pharmaceuticals showed an antagonistic interaction to L. minor. Derived WQC assumed lower values for propranolol than for losartan. The MEC/PNEC ratios showed that propranolol may pose a risk for the most sensitive aquatic species, while acceptable risks posed by losartan were estimated for most of aquatic matrices. To the authors knowledge these are the first data about losartan toxicity for L. minor.

Losartan-induced hypotension leads to tau hyperphosphorylation and memory deficit.

Recent studies have reported a correlation between dementia and low blood pressure. How hypotension is associated with the increased risk of Alzheimer's disease (AD) remains unclear. Here we show that one month treatment of losartan, an angiotensin II type 1 (AT1) receptor antagonist, causes chronic and sustained hypotension, along with oxidative stress in adult male Sprague-Dawley rats. Furthermore, we show that losartan treatment increases the level of inactivated protein phosphatase 2A (PP2A) and the hyperphosphorylation of tau at Ser 199 and Ser 396. Rats treated with losartan present memory deficits and decreases in spine-density. These findings suggest that losartan-induced hypotension may increase the risk of AD-like pathological alteration and behavioral impairment through oxidative stress which leads to tau hyperphosphorylation and loss of dendritic spines.

Postnatal renal abnormalities in rats exposed to losartan during lactation.

BACKGROUND/AIMS: Rats exposed to losartan during lactation exhibit progressive changes in renal function and structure. This study analyzed the early events in pups from dams that received losartan during lactation. METHODS: Male Wistar rats from dams that received 2% sucrose (control, n = 25) or losartan (100 mg/kg/day) diluted in 2% sucrose (n = 33) during lactation were anesthetized 21 days after birth. Blood and urine samples were collected to assess renal function, and kidneys were removed for histological, immunohistochemical, Western blot, lipid peroxidation and glutathione analyses. RESULTS: The group exposed to losartan exhibited increased albuminuria and fractional sodium and potassium excretion, decreased glomerular area and interstitial expansion. Immunohistochemical analyses demonstrated increased tubulointerstitial macrophage infiltration, apoptosis and increased vimentin and α-smooth-muscle-actin expression in animals exposed to losartan. In addition, the glomeruli of animals exposed to losartan exhibited increased peripheral desmin expression and reduced glomerular epithelial protein 1 and podocin expression compared to controls. Lastly, renal lipid peroxidation and glutathione levels were higher in the losartan-treated pups. CONCLUSION: Pups exposed to losartan during lactation exhibited adverse changes in renal function and structure, and tubulointerstitial inflammation at 21 days of age that were associated with apoptosis and oxidative stress.

CYP2C9-mediated metabolic activation of losartan detected by a highly sensitive cell-based screening assay.

Drug-induced hepatotoxicity is a major problem in drug development, and reactive metabolites generated by cytochrome P450s are suggested to be one of the causes. CYP2C9 is one of the major enzymes in hepatic drug metabolism. In the present study, we developed a highly sensitive cell-based screening system for CYP2C9-mediated metabolic activation using an adenovirus vector expressing CYP2C9 (AdCYP2C9). Human hepatocarcinoma HepG2 cells infected with our constructed AdCYP2C9 for 2 days at multiplicity of infection 10 showed significantly higher diclofenac 4'-hydroxylase activity than human hepatocytes. AdCYP2C9-infected cells were treated with several hepatotoxic drugs, resulting in a significant increase in cytotoxicity by treatment with losartan, benzbromarone, and tienilic acid. Metabolic activation of losartan by CYP2C9 has never been reported, although the metabolic activations of benzbromarone and tienilic acid have been reported. To identify the reactive metabolites of losartan, the semicarbazide adducts of losartan were investigated by liquid chromatography-tandem mass spectrometry. Two CYP2C9-specific semicarbazide adducts of losartan (S1 and S2) were detected. S2 adduct formation suggested that a reactive metabolite was produced from the aldehyde metabolite E3179, but a possible metabolite from S1 adduct formation was not produced via E3179. In conclusion, a highly sensitive cell-based assay to evaluate CYP2C9-mediated metabolic activation was established, and we found for the first time that CYP2C9 is involved in the metabolic activation of losartan. This cell-based assay system would be useful for evaluating drug-induced cytotoxicity caused by human CYP2C9.

Prenatal blockade of Ang II receptors affects neonatal rat hindbrain structure and receptor localization.

The development of knock-out mice for Angiotensin II (Ang II) AT(2) receptors, which exhibited altered exploratory behavior, prompted us to investigate the cerebellum and brainstem. We evaluated the effect of stimulation/inhibition of Ang II receptors on hindbrain development, in offspring (postnatal days P0, P8) of pregnant rats treated during late pregnancy (Ang II, Losartan or PD123319, 1 mg/kg/day). Receptor localization by autoradiography showed in P0 and P8 hindbrains, that most structures expressed AT(2) subtype: cerebellar cortex, cerebellar nuclei, genu facial nucleus, inferior colicullus, inferior olive. In the cerebellar cortex, [(125)I]Ang II AT(2) binding was predominant, while low AT(1) binding was observed in adjacent layers of the cerebellar cortex. Blockade of AT(2) receptors with PD123319 increased binding in cerebellar nuclei (p<0.05) and brainstem nuclei at P0, P8, in correlation with increased AT(2) receptor expression by RT-PCR. The enlarged external granular layer (EGL) in PD123319-treated P0 pups contrast with the significant decrease in Ang II binding (p<0.001) in the cerebellar cortex. Blockade of AT(2) receptors during late pregnancy seems to arrest cerebellar cortex development in P0 animals. On the contrary, increased AT(2) binding was observed in cerebellar cortex and DTg nucleus in PD123319-treated P8 animals (p<0.001). Ang II treatment leads to increased binding in the brainstem. In spite of the low doses of Ang II antagonists used, treatments were performed during a time-frame critical for hindbrain development, leading to remarkable effects. The present study makes a contribution to understand the role of Ang II receptors during hindbrain development.

Inhibition of Angiotensin II receptors during pregnancy induces malformations in developing rat kidney.

Evidence suggests that Angiotensin II plays an important role in the complex process of renal organogenesis. Rat kidney organogenesis starts between E13-14 and lasts up to 2 weeks after birth. The present study demonstrates histologic modifications and changes in receptor localisation in animals born from mothers treated with Angiotensin II, Losartan or PD123319 (1.0 mg/kg/day) during late pregnancy. Angiotensin II-treated animals exhibited very well developed tubules in the renal medulla in coincidence with higher AT(1) binding. Control animals exhibited angiotensin AT(2) binding in the outer stripe of the outer medulla, while in the Angiotensin II-treated animals binding was observed to the inner stripe. In Angiotensin II-treated 1-week-old animals, the nephrogenic zone contained fewer immature structures, and more developed collecting tubules than control animals. Treatment with Losartan resulted in severe renal abnormalities. For newborn and 1-week-old animals, glomeruli exhibited altered shape and enlarged Bowman spaces, in concordance with a loss of [(125)I]Angiotensin II binding in the cortex. Blockade with PD123319 led to an enlarged nephrogenic zone with increased number of immature glomeruli, and less glomeruli in the juxtamedullary area. Autoradiography showed a considerable loss of AT(1) binding in the kidney cortex of PD123319-treated animals at both ages. The present results show for the first time histomorphological and receptor localisation alterations following treatment with low doses of Losartan and PD123319 during pregnancy. These observations confirm previous assumptions that in the developing kidney Angiotensin II exerts stimulatory effects through AT(1) receptors that might be counterbalanced by angiotensin AT(2) receptors.

Angiotensin AT1-receptor inhibition exacerbates renal injury resulting from partial unilateral ureteral obstruction in the neonatal rat.

The renin-angiotensin system is activated in the developing kidney and is necessary for normal renal development, but is further activated by unilateral ureteral obstruction (UUO). During nephrogenesis, there is a switch from a preponderance of angiotensin AT(2) to AT(1) receptors in the rat. We examined the renal cellular response to angiotensin II receptor inhibition in the neonatal rat subjected to partial UUO under anesthesia within 48 h of birth. Group I ("early") received saline vehicle, losartan (AT(1) inhibitor), or PD-123319 (AT(2) inhibitor) during the completion of nephrogenesis in the first 10 days of life. Group II ("late") received each of the three treatments throughout the subsequent 10 days of life. Kidneys were harvested at 21 days, and the distribution of renin, apoptosis, macrophages, alpha-smooth muscle actin, and collagen was determined. Losartan and PD-123319 each increased vascular renin distribution in both kidneys. Partial UUO reduced growth and increased apoptosis, macrophages, alpha-smooth muscle actin, and collagen in the obstructed kidney. Early losartan treatment further increased alpha-smooth muscle actin and collagen in the obstructed kidney and induced apoptosis, macrophages, and collagen in the contralateral kidney. Late losartan treatment had no effect on any of the parameters in either kidney, and PD-123319 had no effect on either kidney. We conclude that selective inhibition of AT(1) receptors during nephrogenesis (but not during subsequent renal maturation) exacerbates injury to the obstructed kidney and also injures the contralateral kidney. These results suggest that angiotensin II receptor blockers should be avoided in the developing hydronephrotic kidney.

Comparative study of TA-606, a novel angiotensin II receptor antagonist, with losartan in terms of species difference and orthostatic hypotension.

Losartan is a prodrug type Angiotensin II (Ang II) AT1-receptor antagonist whose efficacy depends on the oxidase activity of individuals. In addition, losartan affects the normal blood pressure and can potentially cause orthostatic hypotension. In this report, we examined effects of TA-606 [(3-pentyloxy)carbonyloxymethyl-5-acetyl-2-n-propyl-3-[2'(1H -tetrazole-5-yl)biphenyl-4-yl]methyl-4,5,6,7-tetrahydro imidazo[4,5-c]pyridine-4-carboxylate hydrochloride], a prodrug type AT1-receptor antagonist, on the Ang II-induced pressor response and hypertension in a dog model, which is known to have lower oxidase activity than other species, and orthostatic hypotension in the rat tilting model. The results indicated that TA-606 was immediately converted to its active form, 606A, after oral administration, and it demonstrated potent inhibition of the Ang II-induced pressor response in conscious normotensive dogs (0.3-3 mg/kg, p.o.). It also had a potent hypotensive effect in conscious 2K,1C-renal hypertensive dogs (0.3-10 mg/kg, p.o.). These effects of TA-606 were 32 and 30 times more potent than those of losartan, respectively. In addition, EXP3174 (1, 10 mg/kg, i.v.), an active metabolite of losartan, but not 606A (1-30 mg/kg, i.v.) showed an orthostatic hypotensive effect in the rat tilting model. These results suggest that TA-606 is an effective Ang II receptor antagonist without the drawbacks of losartan.

Effects of losartan on the sexual behavior of male rats.

Many commonly used antihypertensive drugs such as diuretics and beta-blockers can interfere with sexual function in both sexes, causing loss of libido, impairment of erectile function and ejaculation in men, and delay or prevent orgasm in women. Newly developed antihypertensive drugs should ideally not interfere with the patients' quality of life including sexual function. This study examined the effects of losartan, a nonpeptide, specific antagonist for type I angiotensin II receptors, on the male sexual behavior of rats. Spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats were treated with losartan 30 mg/ kg/day or saline control for 7, 30 and 90 days. Dark-cycle video recording was used to analyze the male sexual activities of the rats. No significant alteration in male sexual performance was observed after 7 and 30 days of treatment with losartan. In contrast, SHRs treated with propranolol 5 mg/kg/day showed increases in intromission latency, ejaculation latency and postejaculatory period indicating decreased libido and erectile and ejaculatory function. Upon completion of 90 days of losartan administration, the mount latency of the SHR was significantly increased, suggesting a decrease in libido although other parameters were unchanged and there was no effect in WKY rats. It is therefore concluded that losartan may have an advantage in preservation of sexual function when used clinically for the treatment of hypertensive disorders.

Contrasting renal effects of chronic administrations of enalapril and losartan on one-kidney, one clip hypertensive rats.

OBJECTIVE: To compare the effects of chronic administrations of the angiotensin II antagonist losartan and of the angiotensin I converting enzyme inhibitor enalapril on renal function in sodium-depleted rats with one-kidney, one clip hypertension, and to examine the contribution of endogenous kinins to the effect of enalapril. METHODS: We administered enalapril and losartan (10 and 30 mg/kg per day, respectively) for 6 days to hypertensive rats that had been subjected to dietary sodium-intake restriction for 6 days prior to treatment and continued to be subjected to this restriction during treatment. In an additional group, administration of enalapril was combined with infusion of the bradykinin B2-receptor antagonist Hoe 140 (300 microg/kg per day subcutaneously via an osmotic pump). Renal function of anesthetized rats was assessed by using a clearance technique. RESULTS: Despite there being similar falls in arterial pressure, glomerular filtration rate (867 +/- 40 microl/min per g kidney weight in untreated rats) was decreased to a larger extent in enalapril-treated than it was in losartan-treated rats (284 +/- 29 versus 438 +/- 36 microl/min per g kidney weight, P < 0.01). Although infusion of Hoe 140 had no influence on the effect of enalapril on arterial pressure, the level of glomerular filtration achieved in rats of this group (545 +/- 55 microl/min per g kidney weight) was similar to that found in losartan-treated rats. No effect of either treatment on renal plasma flow was detected; as a consequence, the excessive decrease in filtration fraction observed for rats in the enalapril-treated group was corrected by concomitant administration of Hoe 140. Interestingly, administration of enalapril resulted in a greater loss of sodium than did administration of losartan (723 +/- 147 versus 308 +/- 57 micromol during 6 days), and this effect was abolished by infusion of Hoe 140 (353 +/- 42 micromol during 6 days). CONCLUSION: Administration of enalapril to sodium-depleted rats with one-kidney, one clip hypertension reduces their glomerular filtration rate to a greater extent than does administration of losartan despite these agents having similar effects on systemic blood pressure. Combined administration of enalapril and Hoe 140 has a less marked effect on glomerular filtration rate than does that of enalapril alone. This suggests that kinins play a role in the regulation of efferent arteriolar tone in this rat model.

The effects of angiotensin II and specific angiotensin receptor blockers on embryonic cardiac development and looping patterns.

The role of angiotensin II (Ang II) in the early embryonic development of the heart has not been examined. We have used RT-PCR to identify mRNA for angiotensinogen, angiotensin-converting enzyme, and the Ang II AT1 and AT2 receptors in embryonic day 10.25 Sprague-Dawley rats, and have used confocal microscopy to localize the AT1 receptor to the greater curvature of the developing ventricle in these animals at embryonic days (ED) 9.25 and 10.25. The antibodies used in immunolocalization studies did not distinguish between the AT1a and AT1b receptor subtypes. In whole embryo culture, Ang II added to the culture media resulted in increased ventricular growth and myocyte hypertrophy when treated embryos were compared to cultured littermate controls. Use of Losartan and PD123,319 to block the Ang II AT1 and AT2 receptors resulted in reduced ventricular development and cardiac dilation when compared to control and Ang II-treated embryos. Addition of Ang II and PD123,319 to the culture media also resulted in cardiac loop inversions which may be associated with disruption of normal myofibrillar development. These results clearly indicate an important role for Ang II in the early embryonic development of the heart.