Phenotypic Characterization of the Endocannabinoid-Degrading Enzyme Alpha/Beta-Hydrolase Domain 6 Knockout Rat.

Introduction: Alpha/beta-hydrolase domain 6 (ABHD6) is an enzyme that hydrolyzes 2-arachidonoylglycerol, a high-efficiency endogenous cannabinoid. Although the endocannabinoid system has been suggested to be involved in regulation of bladder function, the roles of ABHD6 in the control of micturition remain unknown. To elucidate the physiological and pathological roles of ABHD6 in vivo, we examined phenotypes of ABHD6 knockout rats (Abhd6-/-) generated by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated proteins system. Materials and Methods: Age-matched knockout and wild-type (WT) rats of both sexes were used. Results: Expression of ABHD6, assessed by quantitative real-time polymerase chain reaction and Western blot analysis, was clearly diminished in Abhd6-/- rats compared with WT rats. Mutant rats had a normal appearance, and the body weight and food consumption were similar to those of WT rats. The interval between bladder contractions assessed by continuous cystometry was significantly shorter in ABHD6 knockout rats than in WT rats when the bladder was stimulated with acetic acid. Mechanical paw withdrawal thresholds measured by von Frey testing were significantly lowered in the knockout rats than in WT rats. The plasma levels of prostaglandin E2 (PGE2) and the stable metabolite of PGE2 in Abhd6-/- rats were twice as high as that in WT rats. Conclusions: Deletion of the ABHD6 gene in rats causes more frequent urination in the stimulated bladder and hyperalgesia to non-noxious mechanical stimuli along with increased plasma PGE2.

Protective effect of Actinidia arguta in MPTP-induced Parkinson's disease model mice.

Parkinson's disease (PD) is a neurodegenerative disease characterized by the progressive degeneration of dopaminergic neurons in the substantia nigra. Oxidative stress-induced neuronal death has been identified as one of the major causes of nigrostriatal degeneration in PD. The fruit of Actinidia arguta (A. arguta), known as sarunashi in Japan, has been reported to show beneficial health effects such as antioxidant, anti-inflammatory, anti-mutagenic, and anticholinergic effects. In this study, we investigated the neuroprotective effects of A. arguta in 1-methyl-4-phenyl-1,2,3,6-tetrahydropypridine (MPTP)-induced PD model mice. A. arguta juice was administered to 7-week-old C57BL/6J mice continuously for 10 days before the first MPTP injection. The degeneration of dopaminergic neurons in the substantia nigra was induced by MPTP (30 mg/kg, i. p.) once daily for five consecutive days. We found that the administration of A. arguta ameliorated MPTP-induced motor impairment and suppressed the MPTP-induced reductions of tyrosine hydroxylase-positive neurons and tyrosine hydroxylase protein expression in the substantia nigra. Our findings suggest that taking A. arguta could provide neuroprotection that delays or prevents the neurodegenerative process of PD.

Idarubicin, an Anthracycline, Induces Oxidative DNA Damage in the Presence of Copper (II).

BACKGROUND/AIM: The aim of the present study was to investigate whether idarubicin (IDR) induces oxidative DNA damage in the presence of copper (II). MATERIALS AND METHODS: DNA damage was evaluated by pBR322 plasmid DNA cleavage. The formation of oxidative stress markers [O2 •- and 8-hydroxy-2'-deoxyguanosine (8-OHdG)] was analysed. RESULTS: IDR induced DNA damage and O2 •- and 8-OHdG generation in the presence of copper (II). CONCLUSION: IDR induced oxidative DNA damage in the presence of copper (II). Since it has been reported that the concentration of copper in the serum of cancer patients is higher than that in healthy groups, IDR-induced oxidative DNA damage in the presence of copper (II) may play an important role in anticancer therapeutic strategies.

Evaluation of a rat model of functional urinary bladder outlet obstruction produced by chronic inhibition of nitric oxide synthase.

AIMS: Ligation of the urethra to create partial bladder outlet obstruction has widely been used as an animal model of bladder obstruction, although obstructive bladder dysfunction may be due to both mechanical and functional obstruction. Previous studies in rodents have demonstrated that long-term nitric oxide (NO) deficiency can lead to detrusor overactivity, and lack of NO may thus cause impairment of bladder outlet relaxation. The aim of this study was to define the characteristics of bladder and urethral dysfunction induced by chronic NO deficiency through both in vivo and in vitro investigations. MAIN METHODS: Rats were divided into two groups, and one group received an NO synthase inhibitor (Nω-nitro-L-arginine methyl ester hydrochloride: L-NAME) in the drinking water for 4 weeks. Bladder and urethral function were evaluated by continuous cystometry and isovolumetric cystometry. In vitro functional studies of detrusor strips and measurement of the mRNA and protein expression of an ischemic marker and a gap junction protein were also performed in separate rats. KEY FINDINGS: L-NAME administration raised blood pressure and decreased plasma nitrite/nitrate level compared to the control group. L-NAME treatment increased the frequency of bladder contractions and the residual volume, and elevated urethral pressure and bladder contraction pressure. In addition, carbachol-induced contraction was reduced in isolated detrusor strips from the L-NAME group, and bladder expression of HIF-1 and connexin 43 showed upregulation. SIGNIFICANCE: These findings suggest that chronic administration of L-NAME to rats induces bladder hyperactivity with residual urine, and may provide a useful model of functional bladder obstruction.

[Long-term dietary nitrite and nitrate deficiency causes metabolic syndrome, endothelial dysfunction, and cardiovascular death in mice].

Nitric oxide (NO) is synthesized not only from L-arginine by NO synthases (NOSs), but also from its inert metabolites, nitrite and nitrate. Green leafy vegetables are abundant in nitrate, however whether or not a deficiency in dietary nitrite/nitrate spontaneously causes disease remains to be clarified. In this study, we tested our hypothesis that long-term dietary nitrite/nitrate deficiency induces metabolic syndrome (MetS) in mice. To this end, we prepared a low nitrite/nitrate diet (LND) consisting of an amino acid-based low nitrite/nitrate chow in which the contents of L-arginine, fat, carbohydrates, protein, and energy were identical with a regular chow, and potable ultrapure water. Nitrite and nitrate were undetectable in both the chow and the water. Intriguingly, in comparison with a regular diet, 3 months of the LND significantly elicited visceral adiposity, dyslipidaemia, and glucose intolerance; 18 months of the LND significantly provoked increased body weight, hypertension, insulin resistance, and impaired endothelium-dependent relaxations to acetylcholine; and 22 months of the LND significantly led to death due to cardiovascular disease, including acute myocardial infarction. These abnormalities were reversed by simultaneous treatment with sodium nitrate, and were significantly associated with endothelial NOS down-regulation, adiponectin insufficiency, and gut microbiota dysbiosis. These results provide the first evidence that long-term dietary nitrite/nitrate deficiency gives rise to MetS, endothelial dysfunction, and cardiovascular death in mice, indicating a novel pathogenetic role of the exogenous NO production system in MetS and its vascular complications.

Protective Role of Myelocytic Nitric Oxide Synthases against Hypoxic Pulmonary Hypertension in Mice.

RATIONALE: Nitric oxide (NO), synthesized by NOSs (NO synthases), plays a role in the development of pulmonary hypertension (PH). However, the role of NO/NOSs in bone marrow (BM) cells in PH remains elusive. OBJECTIVES: To determine the role of NOSs in BM cells in PH. METHODS: Experiments were performed on 36 patients with idiopathic pulmonary fibrosis and on wild-type (WT), nNOS (neuronal NOS)-/-, iNOS (inducible NOS)-/-, eNOS (endothelial NOS)-/-, and n/i/eNOSs-/- mice. MEASUREMENTS AND MAIN RESULTS: In the patients, there was a significant correlation between higher pulmonary artery systolic pressure and lower nitrite plus nitrate levels in the BAL fluid. In the mice, hypoxia-induced PH deteriorated significantly in the n/i/eNOSs-/- genotype and, to a lesser extent, in the eNOS-/- genotype as compared with the WT genotype. In the n/i/eNOSs-/- genotype exposed to hypoxia, the number of circulating BM-derived vascular smooth muscle progenitor cells was significantly larger, and transplantation of green fluorescent protein-transgenic BM cells revealed the contribution of BM cells to pulmonary vascular remodeling. Importantly, n/i/eNOSs-/--BM transplantation significantly aggravated hypoxia-induced PH in the WT genotype, and WT-BM transplantation significantly ameliorated hypoxia-induced PH in the n/i/eNOSs-/- genotype. A total of 69 and 49 mRNAs related to immunity and inflammation, respectively, were significantly upregulated in the lungs of WT genotype mice transplanted with n/i/eNOSs-/--BM compared with those with WT-BM, suggesting the involvement of immune and inflammatory mechanisms in the exacerbation of hypoxia-induced PH caused by n/i/eNOSs-/--BM transplantation. CONCLUSIONS: These results demonstrate that myelocytic n/i/eNOSs play an important protective role in the pathogenesis of PH.

Long-term dietary nitrite and nitrate deficiency causes the metabolic syndrome, endothelial dysfunction and cardiovascular death in mice.

AIMS/HYPOTHESIS: Nitric oxide (NO) is synthesised not only from L-arginine by NO synthases (NOSs), but also from its inert metabolites, nitrite and nitrate. Green leafy vegetables are abundant in nitrate, but whether or not a deficiency in dietary nitrite/nitrate spontaneously causes disease remains to be clarified. In this study, we tested our hypothesis that long-term dietary nitrite/nitrate deficiency would induce the metabolic syndrome in mice. METHODS: To this end, we prepared a low-nitrite/nitrate diet (LND) consisting of an amino acid-based low-nitrite/nitrate chow, in which the contents of L-arginine, fat, carbohydrates, protein and energy were identical with a regular chow, and potable ultrapure water. Nitrite and nitrate were undetectable in both the chow and the water. RESULTS: Three months of the LND did not affect food or water intake in wild-type C57BL/6J mice compared with a regular diet (RD). However, in comparison with the RD, 3 months of the LND significantly elicited visceral adiposity, dyslipidaemia and glucose intolerance. Eighteen months of the LND significantly provoked increased body weight, hypertension, insulin resistance and impaired endothelium-dependent relaxations to acetylcholine, while 22 months of the LND significantly led to death mainly due to cardiovascular disease, including acute myocardial infarction. These abnormalities were reversed by simultaneous treatment with sodium nitrate, and were significantly associated with endothelial NOS downregulation, adiponectin insufficiency and dysbiosis of the gut microbiota. CONCLUSIONS/INTERPRETATION: These results provide the first evidence that long-term dietary nitrite/nitrate deficiency gives rise to the metabolic syndrome, endothelial dysfunction and cardiovascular death in mice, indicating a novel pathogenetic role of the exogenous NO production system in the metabolic syndrome and its vascular complications.

Effect of caffeine contained in a cup of coffee on microvascular function in healthy subjects.

Recent epidemiological studies have demonstrated that coffee drinking is associated with reduced mortality of cardiovascular disease. However, its precise mechanisms remain to be clarified. In this study, we examined whether single ingestion of caffeine contained in a cup of coffee improves microvascular function in healthy subjects. A double-blind, placebo-controlled, crossover study was performed in 27 healthy volunteers. A cup of either caffeinated or decaffeinated coffee was drunk by the subjects, and reactive hyperemia of finger blood flow was assessed by laser Doppler flowmetry. In an interval of more than 2 days, the same experimental protocol was repeated with another coffee in a crossover manner. Caffeinated coffee intake slightly but significantly elevated blood pressure and decreased finger blood flow as compared with decaffeinated coffee intake. There was no significant difference in heart rate between caffeinated and decaffeinated coffee intake. Importantly, caffeinated coffee intake significantly enhanced post-occlusive reactive hyperemia of finger blood flow, an index of microvascular endothelial function, compared with decaffeinated coffee intake. These results provide the first evidence that caffeine contained in a cup of coffee enhances microvascular function in healthy individuals.

Development of an experimentally useful model of acute myocardial infarction: 2/3 nephrectomized triple nitric oxide synthases-deficient mouse.

We investigated the effect of subtotal nephrectomy on the incidence of acute myocardial infarction (AMI) in mice deficient in all three nitric oxide synthases (NOSs). Two-thirds nephrectomy (NX) was performed on male triple NOSs(-/-) mice. The 2/3NX caused sudden cardiac death due to AMI in the triple NOSs(-/-) mice as early as 4months after the surgery. The 2/3NX triple NOSs(-/-) mice exhibited electrocardiographic ST-segment elevation, reduced heart rate variability, echocardiographic regional wall motion abnormality, and accelerated coronary arteriosclerotic lesion formation. Cardiovascular risk factors (hypertension, hypercholesterolemia, and hyperglycemia), an increased number of circulating bone marrow-derived vascular smooth muscle cell (VSMC) progenitor cells (a pro-arteriosclerotic factor), and cardiac up-regulation of stromal cell-derived factor (SDF)-1α (a chemotactic factor of the progenitor cells) were noted in the 2/3NX triple NOSs(-/-) mice and were associated with significant increases in plasma angiotensin II levels (a marker of renin-angiotensin system activation) and urinary 8-isoprostane levels (a marker of oxidative stress). Importantly, combined treatment with a clinical dosage of an angiotensin II type 1 receptor blocker, irbesartan, and a calcium channel antagonist, amlodipine, markedly prevented coronary arteriosclerotic lesion formation and the incidence of AMI and improved the prognosis of those mice, along with ameliorating all those pro-arteriosclerotic parameters. The 2/3NX triple NOSs(-/-) mouse is a new experimentally useful model of AMI. Renin-angiotensin system activation, oxidative stress, cardiovascular risk factors, and SDF-1α-induced recruitment of bone marrow-derived VSMC progenitor cells appear to be involved in the pathogenesis of AMI in this model.

Long-term treatment with san'o-shashin-to, a kampo medicine, markedly ameliorates cardiac ischemia-reperfusion injury in ovariectomized rats via the redox-dependent mechanism.

BACKGROUND: Hormone replacement therapy has failed to reduce ischemic cardiovascular events in climacteric women. To explore alternative therapy, we examined whether san'o-shashin-to (TJ-113), a kampo medicine, ameliorates cardiac ischemia-reperfusion (IR) injury in a climacteric rat model. METHODS AND RESULTS: Cardiac function and infarct size after IR were significantly exacerbated in ovariectomized rats as compared with sham-operated rats, whereas long-term treatment with a clinical dosage of TJ-113 for 4 weeks markedly improved these functional and morphological changes. Myocardial inducible nitric oxide synthase (iNOS) expression and peroxynitrite levels were significantly higher in ovariectomized rats compared with sham-operated rats, and long-term TJ-113 treatment significantly reduced these oxidative changes. Furthermore, myocardial manganese superoxide dismutase (Mn-SOD) activity was significantly lower in ovariectomized than in sham-operated rats, and long-term TJ-113 treatment significantly restored antioxidant activity. Importantly, those beneficial actions of TJ-113 were significantly inhibited by the estrogen receptor antagonist, fulvestrant, and the phytoestrogen, emodin, a TJ-113 ingredient, mimicked the actions of TJ-113, suggesting involvement of emodin in the effects of TJ-113. CONCLUSIONS: These results provide the first evidence that long-term treatment with a clinical dosage of TJ-113 markedly ameliorates cardiac IR injury in ovariectomized rats via inhibition of iNOS expression, suppression of peroxynitrite formation, and restoration of Mn-SOD activity. TJ-113 may be a novel therapeutic option in the treatment of ischemic heart disease in climacteric women.

Crucial vasculoprotective role of the whole nitric oxide synthase system in vascular lesion formation in mice: Involvement of bone marrow-derived cells.

Although all three nitric oxide (NO) synthases (nNOS, iNOS, and eNOS) are expressed in injured arteries, it remains to be elucidated the role of the NOSs in their entirety in the vascular lesion formation. We addressed this issue in mice deficient in all NOS genes. Vascular injury was induced by permanent ligation of a unilateral carotid artery in wild-type (WT), singly, and triply NOS(-/-) mice. Two weeks after the procedure, constrictive vascular remodeling and neointimal formation were recognized in the ligated arteries. While constrictive remodeling was noted in the nNOS(-/-) and iNOS(-/-) genotypes, it was most accelerated in the n/i/eNOS(-/-) genotype. While neointimal formation was evident in the eNOS(-/-) and nNOS(-/-) genotypes, it was also most aggravated in the n/i/eNOS(-/-) genotype. Those lesions were reversed by long-term treatment with isosorbide dinitrate, a NO donor. Finally, we examined the involvement of bone marrow-derived cells in the vascular lesion formation. Bone marrow from the WT, singly, or triply NOS(-/-) mice was transplanted into the WT mice, and then the carotid ligation was performed. Intriguingly, constrictive remodeling and neointimal formation were both similarly most exacerbated in the case of the n/i/eNOS(-/-) bone marrow transplantation. These results indicate that the complete disruption of all the NOS genes causes markedly accelerated vascular lesion formation caused by blood flow disruption in mice in vivo, demonstrating the crucial vasculoprotective role of the whole endogenous NOS system. Our findings also suggest that the NOS system in bone marrow-derived cells may be involved in this vasculoprotective mechanism.

Increasing dihydrobiopterin causes dysfunction of endothelial nitric oxide synthase in rats in vivo.

An elevation of oxidized forms of tetrahydrobiopterin (BH(4)), especially dihydrobiopterin (BH(2)), has been reported in the setting of oxidative stress, such as arteriosclerotic/atherosclerotic disorders, where endothelial nitric oxide synthase (eNOS) is dysfunctional, but the role of BH(2) in the regulation of eNOS activity in vivo remains to be evaluated. This study was designed to clarify whether increasing BH(2) concentration causes endothelial dysfunction in rats. To increase vascular BH(2) levels, the BH(2) precursor sepiapterin (SEP) was intravenously given after the administration of the specific dihydrofolate reductase inhibitor methotrexate (MTX) to block intracellular conversion of BH(2) to BH(4). MTX/SEP treatment did not significantly affect aortic BH(4) levels compared with control treatment. However, MTX/SEP treatment markedly augmented aortic BH(2) levels (291.1 ± 29.2 vs. 33.4 ± 6.4 pmol/g, P < 0.01) in association with moderate hypertension. Treatment with MTX alone did not significantly alter blood pressure or BH(4) levels but decreased the BH(4)-to-BH(2) ratio. Treatment with MTX/SEP, but not with MTX alone, impaired ACh-induced vasodilator and depressor responses compared with the control treatment (both P < 0.05) and also aggravated ACh-induced endothelium-dependent relaxations (P < 0.05) of isolated aortas without affecting sodium nitroprusside-induced endothelium-independent relaxations. Importantly, MTX/SEP treatment significantly enhanced aortic superoxide production, which was diminished by NOS inhibitor treatment, and the impaired ACh-induced relaxations were reversed with SOD (P < 0.05), suggesting the involvement of eNOS uncoupling. These results indicate, for the first time, that increasing BH(2) causes eNOS dysfunction in vivo even in the absence of BH(4) deficiency, demonstrating a novel insight into the regulation of endothelial function.

Complete disruption of all nitric oxide synthase genes causes markedly accelerated renal lesion formation following unilateral ureteral obstruction in mice in vivo.

The role of nitric oxide (NO) derived from all three NO synthases (NOSs) in renal lesion formation remains to be fully elucidated. We addressed this point in mice lacking all NOSs. Renal injury was induced by unilateral ureteral obstruction (UUO). UUO caused significant renal lesion formation (tubular apoptosis, interstitial fibrosis, and glomerulosclerosis) in wild-type, singly, and triply NOS(-/-) mice. However, the extents of renal lesion formation were markedly and most accelerated in the triply NOS(-/-) genotype. UUO also elicited the infiltration of inflammatory macrophages, up-regulation of transforming growth factor (TGF)-ß1, and induction of epithelial mesenchymal transition (EMT) in all of the genotypes; however, the extents were again largest by far in the triply NOS(-/-) genotype. Importantly, long-term treatment with the angiotensin II type 1 (AT(1))-receptor blocker olmesartan significantly prevented the exacerbation of those renal structural changes after UUO in the triply NOS(-/-) genotype, along with amelioration of the macrophage infiltration, TGF-ß1 levels, and EMT. These results provide the first evidence that the complete disruption of all NOS genes results in markedly accelerated renal lesion formation in response to UUO in mice in vivo through the AT(1)-receptor pathway, demonstrating the critical renoprotective role of all NOSs-derived NO against pathological renal remodeling.

Improvement of impaired endothelial function by tetrahydrobiopterin in stroke-prone spontaneously hypertensive rats.

To investigate the role of tetrahydrobiopterin (BH4), an essential cofactor of nitric oxide synthase, in endothelial function in a model of genetic hypertension, acetylcholine- and sodium nitroprusside (SNP)-induced vasodilator responses were examined in the absence and presence of BH4 in age-matched adult stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto (WKY) rats. Acetylcholine-induced depressor responses attenuated significantly in SHRSP compared with those in WKY rats. Acetylcholine-induced relaxations in phenylephrine-precontracted aortic rings of SHRSP were also significantly impaired as compared to those of WKY rats, while SNP-induced relaxations were similar between both strains. In SHRSP, intravenous infusion of BH4 (0.12 mg/kg per min for 20 min following a bolus injection of 0.48 mg/kg) significantly improved vasodilator responses to acetylcholine without affecting those to SNP, but in WKY rats BH4 did not influence those to acetylcholine. BH4 infusion itself had no hemodynamic effect in both strains. However, BH4 levels in plasma and thoracic aorta as well as plasma concentrations of nitrite plus nitrate, metabolites of NO, in SHRSP were all significantly greater than those in WKY rats, suggesting the occurrence of compensatory upregulation of NO synthesis in SHRSP. These results demonstrate that the impaired endothelial function in SHRSP cannot be explained simply by the decrease in absolute amount of BH4.

Effect of decreased levels of intrinsic tetrahydrobiopterin on endothelial function in anesthetized rats.

Tetrahydrobiopterin (BH4) deficiency has been suggested to be an important factor in vascular endothelial dysfunction. In this study, we investigated the influence of decreased BH4 level produced by administration of 2,4-diamino-6-hydroxypyrimidine (DAHP), a specific inhibitor of the rate-limiting enzyme of BH4 synthesis, on vascular endothelial function in anesthetized rats. Wistar rats were given DAHP (0.1 - 1.0 g/kg, i.p.) or the vehicle 5 h before the experiment. Depressor responses to the endothelium-dependent vasodilator acetylcholine and the endothelium-independent vasodilator sodium nitroprusside were tested. After the experiment, blood and thoracic aorta were taken for estimating their BH4 levels and plasma concentrations of nitrite plus nitrate. DAHP produced marked decreases in BH4 levels in plasma and aorta in a dose-related manner. Baseline values for hemodynamics were not affected by DAHP. Depressor responses to acetylcholine were attenuated with the highest dose of DAHP (1.0 g/kg) but not with DAHP (0.3 g/kg), although similar decreases in BH4 levels were seen with these two doses of DAHP. Treatment with DAHP at each dose did not decrease plasma concentrations of nitrite plus nitrate. These findings suggest that a decrease in BH4 levels by acute inhibition of de novo BH4 synthesis does not necessarily cause endothelial dysfunction.

Effects of landiolol on mechanical and metabolic changes in rat reperfused ischaemic hearts.

1. The aim of the present study was to clarify the effects of landiolol, a short-acting selective beta(1)-adrenoceptor blocking agent, on mechanical and metabolic changes in postischaemic perfused hearts. 2. Rat isolated hearts (n = 30) were randomly separated into non-ischaemic or ischaemic groups. The latter group was further divided into Krebs'-Henseleit solution (KHS)- and landiolol (30, 100 or 300 micromol/L)-treated groups. Ischaemic hearts were subjected to 25 min global ischaemia and 20 min reperfusion under atrial pacing. Time-course changes in left ventricular (LV) end-diastolic pressure (LVEDP), LV developed pressure (LVDP), peak positive velocity of change of LV pressure (LVdP/dt(max)) and coronary flow were observed along with tissue contents of adenosine triphosphate (ATP), creatine phosphate, inorganic phosphate (Pi), malondialdehyde (MDA) and lactate dehydrogenase (LDH) release in coronary effluent. The effects of landiolol on rat isolated aortic preparations under KCl contraction were also investigated. 3. Ischaemia-reperfusion significantly impaired cardiodynamics, such as LVEDP, LVDP and LVdP/dt(max), decreased myocardial ATP content and increased Pi and LDH release. In the 30 micromol/L landiolol-treated group, cardiovascular parameters impaired by ischaemia-reperfusion and increased LDH release were further exacerbated and myocardial MDA content was significantly increased. In the 300 micromol/L landiolol-treated group, cardiac contractile dysfunction was improved and myocardial MDA, ATP and Pi contents were preserved. All measurements in the 100 micromol/L landiolol-treated group were similar to those in the ischaemic KHS group. Furthermore, significant relaxations of isolated aortic preparations were obtained with landiolol 30-1000 micromol/L, suggesting a possible calcium antagonism with landiolol. 4. In conclusion, landiolol, at low concentrations, aggravated myocardial ischaemia-reperfusion injuries, whereas at high concentrations it ameliorated them. The former effect may be mediated by the production of reactive oxygen species, whereas the latter may involve calcium antagonist activity.

Prostacyclin causes splenic dilation and haematological change in dogs.

1. The effect of vasodilators on spleen volume and the blood storage function is not yet well elucidated. To this end, in the present study the effects of prostacyclin, a potent vasodilator, on splenic diameter and blood cell concentrations in arterial and splenic venous blood were evaluated in anaesthetized dogs. 2. The main splenic artery and vein were dissected for measurement of splenic arterial blood flow and intra-arterial administration and for sampling of splenic venous blood, respectively. The diameter of the spleen was measured continuously by sonomicrometry. Counts of white blood cells (WBC), red blood cells (RBC) and platelets in blood sampling from the aorta and splenic vein were estimated by an automatic blood cell counter. 3. Bolus injections of prostacyclin (1-100 ng/kg) into the splenic artery produced dose-dependent increases in splenic arterial blood flow and splenic diameter associated with significant decreases in splenic venous concentrations of WBC, RBC and platelets. When splenic blood flow was kept constant, similar changes in splenic diameter and blood cell counts were observed with prostacyclin injection. 4. Splenic dilation and haematological changes induced by prostacyclin were relatively more potent than those induced by prostaglandin E(2), acetylcholine, nitroglycerin or isoproterenol when doses producing a comparable increase in splenic blood flow were compared. 5. Infusion of prostacyclin (100 ng/kg per min) into the splenic artery caused a marked increase in splenic diameter, with immediate reductions in splenic venous concentrations of WBC, RBC and platelets, followed by significant reductions in these cell counts in the general circulation. 6. These results indicate that prostacyclin produces potent and flow-independent splenic dilation that may contribute to a decrease in circulating blood cell concentrations.

Cardiovascular effects and lethality of venom from nematocysts of the box-jellyfish Chiropsalmus quadrigatus (Habu-kurage) in anaesthetized rats.

Haemodynamic effects of saline-extracted venom from nematocysts isolated from Chiropsalmus quadrigatus (Habu-kurage) were studied in anaesthetized rats. Intravenous administration of venom (0.2-5 microg protein/kg) produced immediately dose-dependent hypertension and bradycardia. Femoral blood flow transiently increased but calculated femoral vascular conductance decreased. Changes caused by 1 microg/kg of venom were reproducible, and were not affected by prazosin, atropine or BQ123 (ET(A) receptor antagonist) but were significantly attenuated by nicardipine. At doses over 2 microg/kg, hypotension and a decrease in pulse pressure were observed subsequent to transient hypertension. In 5 of 8 rats received 5 microg/kg venom and 6 of 6 rats at 10 microg/kg, death due to irreversible cardiac arrest occurred within 30 min after intravenous injection. However, during nicardipine infusion, venom (10 microg/kg) exerted only modest effects and the rats survived. Heating venom (50 degrees C for 10 min) before injection practically abolished the haemodynamic effects of 10 microg/kg venom, indicating its thermolability. Data show that C. quadrigatus venom has both vasoconstrictor and cardiodepressive effects in rats, and suggest that a calcium channel blocker can protect against the cardiovascular and lethal effects of the venom.

Haemodynamic effects of the crude venom from nematocysts of the box-jellyfish Chiropsalmus quadrigatus (Habu-kurage) in anaesthetized rabbits.

Haemodynamic effects of saline-extracted venom from nematocysts isolated from tentacles of the box-jellyfish Chiropsalmus quadrigatus (Habu-kurage) were investigated. In anaesthetized rabbits, i.v. injections of the venom produced hypotension following a transient hypertension. Mean femoral arterial blood flow markedly decreased immediately after the injection and femoral vascular resistance increased. Left ventricular dP/dt remarkably decreased after a transient and small increase, and heart rate decreased. Left ventricular end-diastolic pressure markedly elevated. All of the above changes by 0.2-5 microg/kg of the venom expressed as the amount of protein were seen dose-dependently and occurred without tachyphylaxis. In five of seven animals received an injection of the venom at 10 microg/kg, irreversible cardiac arrest occurred. Changes produced by 1 or 2 microg/kg of the venom were significantly attenuated either by heating the venom at 40 degrees C for 10min or by pretreatment with diltiazem. These results indicate that the venom from Habu-kurage has both vasoconstrictor and cardiodepressive effects, and suggest that these thermolabile actions may be due partly to activation of voltage-dependent calcium channels and probably subsequent calcium-overload.

Cardioprotective effects of extracts from Psidium guajava L and Limonium wrightii, Okinawan medicinal plants, against ischemia-reperfusion injury in perfused rat hearts.

The aim of this study was to determine whether the medicinal herbs growing in Okinawa and possessing a radical-scavenging activity would exert cardioprotective effects against ischemia-reperfusion injury using isolated perfused rat hearts. Effects of the aqueous extracts from Psidium guajava L. and Limonium wrightii at concentrations having an equipotent radical-scavenging activity on myocardial injury produced by global ischemia followed by reperfusion were tested and were further compared with those of quercetin and gallic acid, major antioxidative components of P. guajava L. and L. wrightii, respectively. Both extracts significantly attenuated ischemic contracture during ischemia and improved myocardial dysfunction after reperfusion. Decreases in high-energy phosphates and increases in malondialdehyde in the reperfused hearts were significantly lessened with both plant extracts. Quercetin and gallic acid also exerted similar beneficial effects. These results indicate that P. guajava L. and L. wrightii both have cardioprotective effects against myocardial ischemia-reperfusion injury in isolated rat hearts, primarily through their radical-scavenging actions.