Search

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.

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.

The influence of extracellular Ca 2+ concentration on contractile responses of aortae isolated from diabetic rats to KCl and α-adrenoceptor agonists was compared with that of non-diabetic rat aortae. Diabetic rats 6 weeks after administration of streptozotocin showed significantly lower body weight and higher plasma glucose concentration, but the protein content per each aortic ring preparation was not significantly different from that of non-diabetic preparation. Both diabetic and non-diabetic aortae showed concentration-dependent contractile responses to norepinephrine, which were concentration-dependently inhibited by prazosin. On the other hand, Clonidine induced small contractions in both aortae, which tended to be more inhibited by prazosin than yohimbine. In non-diabetic aortae, the contractile responses to KCl, norepinephrine, methoxamine and Clonidine were significantly greater with 2.5 mmol/l of extracellular Ca 2+ than 1.25 mmol/l. In diabetic aortae, however, the contractile responses were not significantly influenced by changes in extracellular Ca 2+ concentration. Additionally, the contractile responses to each agonist were markedly greater in non-diabetic aortae than diabetic ones. The present results indicate that the contractions of diabetic vasculature do not respond to changes in extracellular Ca 2+ concentration, suggesting that there may be some impairment of Ca 2+ related mechanisms.

An elevation of oxidized forms of tetrahydrobiopterin (BH4), especially dihydrobiopterin (BH2), 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 BH2in the regulation of eNOS activity in vivo remains to be evaluated. This study was designed to clarify whether increasing BH2concentration causes endothelial dysfunction in rats. To increase vascular BH2levels, the BH2precursor sepiapterin (SEP) was intravenously given after the administration of the specific dihydrofolate reductase inhibitor methotrexate (MTX) to block intracellular conversion of BH2to BH4. MTX/SEP treatment did not significantly affect aortic BH4levels compared with control treatment. However, MTX/SEP treatment markedly augmented aortic BH2levels (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 BH4levels but decreased the BH4-to-BH2ratio. 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 BH2causes eNOS dysfunction in vivo even in the absence of BH4deficiency, demonstrating a novel insight into the regulation of endothelial function.

Drug interaction between rizatriptan benzoate, an anti-migraine agent, and sodium valproate (VPA-Na), an anticonvulsant, was studied in rats. When rizatriptan benzoate was administered orally immediately after VPA-Na oral administration, the pharmacokinetic parameters, such as plasma valproic acid (VPA) and area under the plasma concentration-time curve up to 3 h (AUC0–3), were significantly decreased compared with those in the control group. However, when rizatriptan benzoate was administered intraperitoneally immediately after VPA-Na orally, these parameters were not changed. In addition, when benzoic acid was administered orally immediately after VPA-Na orally, these were significantly lower compared with the control values. Therefore, it might be possible that VPA transport by monocarboxylate transporter was competitively inhibited by rizatriptan benzoate and thus absorption of VPA was decreased.

The drug interactions between tandospirone citrate,a non-benzodiazepine antianxiety drug,and oxazolam,a minor benzodiazepine tranquilizer and antianxiety agent,and valpronic acid (VPA),an anti-convulsant,were studied in rats.When tandospirone citrate or citric acid was administered orally immediately following oral administration (p.o.) of sodium valproate (VPA-Na),the plasma VPA levels were significantly lower than those in the control.In addition,pharmacokinetic parameters such as plasma VPA concentration and area under the plasma concentration-time curve up to 3 hr (AUC) were significantly decreased.However,when tandospirone citrate was administered intraperitonally,or both it and oxazolam were administered orally with VPA-Na,the VPA pharmacokinetic parameters were unchanged.These results suggest that decreases in plasma VPA concentrations (including those for AUC) may be due to a reduction in VPA-Na adsorption from the intestinal tract due to tandospirone citrate.

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.

Vascular endothelial dysfunction has been demonstrated in obesity, but the molecular basis for this link has not been clarified. We examined the role of free fatty acids (FFA) on vascular reactivity in the obese fa/fa Zucker diabetic fatty (ZDF) rat. Addition of acetylcholine produced a dose-dependent relaxation in aortic rings of ZDF and lean +/+ rats, but the ED50 value was higher in ZDF (−6.80 ± 0.05 vs. −7.11 ± 0.05 log10 mol/liter, P = 0.033). A 2-wk treatment with a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, pitavastatin (3 mg/kg/d) or a reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, apocynin (5 mmol/liter in drinking water), improved the response in ZDF (ED50, −7.16 ± 0.03 and −7.14 ± 0.05 log10 mol/liter, P = 0.008 and P = 0.015 vs. vehicle, respectively). Vasodilator response to sodium nitroprusside was identical between ZDF and +/+ rats. Vascular reactive oxygen species (ROS) levels and NADPH oxidase activity in aorta were increased in ZDF rats but were decreased by pitavastatin. In in vitro cell culture, intracellular ROS signal and NADPH oxidase subunit mRNA were increased by palmitate, but this palmitate-induced ROS production was inhibited by NADPH oxidase inhibitor or pitavastatin. In conclusion, FFA-induced NADPH oxidase subunit overexpression and ROS production could be involved in the endothelial dysfunction seen in obese ZDF rats, and this could be protected by pitavastatin or NADPH oxidase inhibitors.

The effect of timing on the administration of spherical charcoal (Kremezin) on the pharmacokinetics of valproic acid (VPA) in the coadministration of sodium valproate and Kremezin was examined in rats.Kremezin, when administered either immediately or 30 min after the administration of sodium valproate, significantly decreased the area under the plasma concentration-time curve (AUC) 0-3 of VPA by about 30%. In addition, when Kremezin was administered 30 min or 1 hr before sodium valproate dosing it decreased the maximum plasma concentration (Cmax) of VPA by 39% and 27%, respectively, and significantly decreased the AUC0-3 of VPA by 54% and 45%, respectively. The plasma VPA concentrations in all Kremezin-treated groups were significantly lower than those in the controls. However, Kremezin administered 1 hr after sodium valproate dosing had no effect on the plasma VPA concentration, Cmax or AUC0-3 of VPA.These results suggest that Kremezin decreased the absorption of VPA due to adsorption after the coadministration of sodium valproate and Kremezin.

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.

In order to protect the heart from unfavorable conditions such as myocardial ischemia or heart failure, it seems necessarily to investigate what components are related to such conditions or what drugs affect them. For this purpose, at symposium No. 40 "Recent Advances in Cardiac Protection" at the 75th Annual Meeting of The Japanese Pharmacological Society held in Kumamoto City, the following 6 studies were presented: (1) The Role of Sarcoglycan Complex in Chronic Heart Failure (H. Yoshida et al.); (2) Heart Failure and Proinflammatory Cytokines (T. Kubota et al.); (3) Fundamental Strategies and Current Topics for Cardiac Protection During Open-Heart Surgery (R. Tominaga et al.); (4) Role of Tetrahydrobiopterin in Myocardial Ischemia/ Reperfusion Injury (K. Noguchi et al.); (5) Cardiac Protection by Nitric Oxide (T. Obata); (6) Reconsideration of Anti-oxidants as Protective Drugs on Ischemic Myocardium (K. Ichihara et al.). This review gathers the reports of studies presented at this symposium.

Drug interaction between meropenem (MEPM), a carbapenem of antibiotic agent, and sodium valproate (VPA), an anticonvulsant, was studied in rats and human volunteers. When sodium VPA and MEPM were administered simultaneously, the plasma VPA level was significantly lower and the blood cell/plasma VPA concentration ratio was significantly higher than after the administration of sodium VPA alone (control). Following the simultaneous administration of sodium VPA and MEPM, the pharmacokinetic parameters such as plasma VPA, volume of distribution (Vd) and clearance (CL) were significantly increased, while the maximum plasma concentration (Cmax) and area under the plasma concentration- time curve (AUC) till 3 h were significantly decreased. The ratio of free (unbound) VPA to protein-bound VPA was significantly increased after the administration of MEPM. The concentration of VPA in brain tissue was significantly decreased after the simultaneous administration of VPA and MEPM. Competition between VPA and MEPM for a protein binding site resulted in increased plasma levels of free (unbound) VPA, which then distributed to various tissues, in particular, the blood cells, liver and kidney. VPA which distributed to the liver was metabolized there and excreted. Subsequently, the levels of VPA in the plasma and brain would be significantly decreased.

Effects of salicylate on the pharmacokinetics of valproic acid (VPA) after oral administration (p.o.) of sodium valproate were investigated in rats. When salicylic acid was administered orally after sodium valproate p.o., the plasma VPA concentrations including maximum plasma concentration (C max ), area under the plasma concentration-time curve up to 3 h (AUC 0-3 ) and the elimination half-life ( t 1/2 ) of VPA were lower than control values. In addition, when salicylate was administered intraperitoneally or intravenously, the plasma VPA concentrations, AUC 0-3 and t 1/2 of VPA were lower than those in the control group. These results suggest that decreases in the plasma VPA concentrations including C max and AUC 0-3 with simultaneous oral administration of sodium valproate and salicylic acid may be related to both reduction of absorption and increase in clearance of VPA.

The effect of two kinds of 1,4-dihydropyridine calcium-channel blockers, nicardipine hydrochloride and nifedipine, on the disposition of carvedilol, was studied in rats. Blood samples were assayed for carvedilol levels using solid-phase extraction and high-performance liquid chromatography. The plasma carvedilol concentration was found to be significantly higher, and the area under the concentration-time curve up to 24 h (AUC0→24) was 6.7 and 3.0 times higher after simultaneous oral administration of 20 mg kg−1 carvedilol with 40 mg kg−1 nicardipine hydrochloride, or with 40 mg kg−1 nifedipine, respectively, than after administration of carvedilol alone. The pharmacokinetic interaction between carvedilol and dihydropyridine calcium-channel blockers is thought to be attributable to vasodilator-induced changes in hepatic first-pass metabolism, inhibition in the absorption barrier by P-glycoprotein and in the metabolism of carvedilol.

The purpose of the present study was to evaluate the pharmacokinetic interaction in rats between carvedilol and three kinds of dihydropyridine calcium-channel blockers, including nicaldipine hydrochloride, nifedipine and felodipine by high-performance inquid chromatography using a solid phase extraction column. The plasma crvedilol concentrations were found to be significantly higher than the control levels at 30 min-24 hr and 3-8 hr after the simultaneous administration of 20 mg/kg carvedilol and 40 mg/kg nicaldipine hydrochloride and 40 mg/kg nifedipine, respectively. In addition, the drug pharmacokinetic parameters, comprising the area under the concentration-time curve up to 24 hours (AUC0-24), were 6.7 and 3.0 times higher after the administration of both carvedilol and nicaldipine hydrochloride and nifedipine, respectively. In contrast, after the administration of carvedilol and 5 mg/kg felodipine, the AUC0-24 showed no change.These changes are though to be attributable to either the vasodilator-induced changes in the hepatic first-pass metabolism or the metabolic inhibition.

The pharmacokinetic interaction between carvedilol, a nonselective β-blocking agent and amlodipine besilate, a dihydropyridine calcium-channel blocker were investigated in rats. To determine the concentration-time profile of plasma carvedilol, blood samples were obtained from the tail vein after the oral administration of carvedilol either with or without amlodipine besilate. The plasma carvedilol concentrations and pharmacokinetic parameters, comprising the area under the concentration-time curve from 0 to 24 hours (AUC0-24) showed no changes after the simultaneous oral administration of 20 mg/kg carvedilol and 5 mg/kg amlodipine besilate. In contrast, the plasma carvedilol concentrations at 6 hr-12 hr and AUC0-24 after the oral administration of carvedilol with 40 mg/kg amlodipine besilate were significantly higher than those without amlodipine besilate.These results suggested the pharmacokinetic interaction between carvedilol and amlodipine to be dependent on the dose of amlodipine.

We investigated the effects of metoclopramide and propantheline bromide on the bioavailability of carvedilol in rats. To determine the concentration-time profile of plasma carvedilol, the blood samples were obtained from the tail vein after the simultaneous administration of 20mg/ kg carvedilol either with or without 5 mg/kg metoclopramide and 15 mg/kg propantheline bromide. The plasma carvedilol concentrations were significantly higher than the controls at 15 min.-1 hr and 3, 4 hr, and the drug pharmacokinetic parameters time to Cmax (Tmax) was 0.45 time shorter, while the absorption rate constant (Ka) and area under the concentration-time curve(AUC0-24) were 2.5 and 1.5 times higher after the oral administration of carvedilol with metoclopramide. The rate of bioavailability for carvedilol was accelerated by metoclopramide which stimulates gastric emptying. In contrast, the plasma carvedilol concentrations and Tmax., A UC0-24 did not change after the single intraperitoneal administration of carvedilol with the oral administration of metoclopramide. Conversely, propantheline bromide, which delays gastric emptying, slowed absorption, but not according the AUC0-24 of carvedilol.Other similar pharmacokinetic interaction probably occur since carvedilol are poorly absorbed from the stomach and numerous therapeutic agents influence gastrointestinal motility.

We studied the use of high-performance liquid chromatography (HPLC) with a spectroflurometric detector, using a solid-phase extraction column (Bond Elut cartridge column), for the simple, rapid and sensitive determination of plasma fleroxacin (FLRX) levels in rats. Extracted aliquots were analyzed by HPLC, using a reverse phase octadecyl silica column. The analytical mean recovery of FLRX added to the blank plasma averaged 101.4%. The detection limit was 58 ng/ml in the plasma. The reproducibilities (C.V.) were 0.50-3.22% in the within-day assay and 2.87 C.V.% in the between-day assay, indicating that the analysis method was effective in the determination of FLRX plasma levels.

1. Platelet-activating factor (PAF) is a phospholipid mediator with potent cardiovascular and haematological actions. But its mechanisms of action in vivo have not been fully elucidated, probably due to difficulties arising from previous findings that the effects of PAF are largely mediated by the release of a variety of other autacoids. In the present study, the roles of nitric oxide and eicosanoids in the effects of PAF (0.01-0.25 microgram kg-1 i.v.) on systemic and pulmonary vasculatures and circulating blood cell count were pharmacologically evaluated in anaesthetized dogs. 2. Higher doses of PAF (> 0.1 microgram kg-1) produced a biphasic systemic hypotension. The first hypotension seen 30 s after the injection was accompanied by a decrease in systemic vascular resistance, thrombocytopenia and leukopenia, while the second hypotension seen 1-2 min after PAF was accompanied by a marked rise in pulmonary vascular resistance and decreases in aortic blood flow and cardiac contractility. Lower doses of PAF (0.01 - 0.05 microgram kg-1) caused only the first responses in a dose dependent manner. 3. Pretreatment with indomethacin inhibited the second responses to PAF without affecting the first responses. The thromboxane A2/prostaglandin H2 (TP)-receptor antagonist vapiprost blocked the PAF-induced rise in pulmonary vascular resistance. AA-861, a 5-lipoxygenase inhibitor, attenuated the PAF-induced cardiac depression. The nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester inhibited the PAF-induced early decrease in systemic vascular resistance. 4. All observed changes in haemodynamics and blood cell count after PAF were almost abolished by TCV-309, a PAF-receptor antagonist. 5. Reproducible hypotension and thrombocytopenia produced by a lower dose of PAF (0.05 microgram kg-1) were respectively attenuated and potentiated by pretreatment with NG-nitro-L-arginine, another nitric oxide synthase inhibitor. Administration of L-arginine reversed the effects of the nitric oxide synthase inhibitor. 6. These results indicate that PAF-receptor-mediated production of not only eicosanoids but also nitric oxide may contribute to the cardiovascular and haematological responses to PAF in the dog.

The relationship between cardiac dysfunction and glycogen level and/or duration of diabetes was examined during underperfusion (2 ml/min/g heart weight) with 10(-6)M norepinephrine (NE) in isolated 1- and 6-week streptozotocin-diabetic rat (diabetes mellitus, DM) hearts and non-DM hearts. Glycogen levels in non-DM and 1- and 6-week DM hearts were 85, 120, and 206 mumol/g dry weight, respectively, in the subendocardium. About 13 min after the start of underperfusion with NE, the diastolic tension in 1-week DM hearts began to increase when the glycogen level had decreased to half; in 6-week DM hearts, glycogen decreased more markedly without greater lactate accumulation, but these glycogen levels were still higher (104 mumol/g dry weight) than those in 1-week DM hearts and the diastolic tension did not increase. About 17 min after the onset of underperfusion, the glycogen decreased to the 13-min level of 1-week DM hearts (64 mumol/g dry weight) and the diastolic tension began to increase. Until 20 min after the onset of underperfusion, the injury was less in 6-week than in 1-week DM hearts. However, after 60-min underperfusion with NE, when the glycogen level was markedly low in both groups ( < 20 mumol/g dry weight), diastolic tension was increased twice as much in 6-week DM as in 1-week DM hearts and was related to the decreased subendocardial ATP level. The results indicate that the markedly high glycogen content in diabetic hearts probably helps delay the start of the increase in left ventricular (LV) stiffness during underperfusion with NE. Ultimately, however, the degree of the injury depends on the duration, i.e., the severity, of the diabetes.

The effect of ex vivo insulin on contractile and energy metabolism dysfunctions was examined during hypoperfusion (0.6 ml/min per g heart weight) with 10(-6) M norepinephrine in isolated non-diabetic and streptozotocin-diabetic rats hearts. Insulin (2 mU/min per g heart weight) was infused for 15 min before as well as during 60-min hypoperfusion. Insulin significantly reduced the elevated diastolic tension in diabetic hearts (from 3.8 to 0.7 delta g), but not in non-diabetic hearts (from 1.4 to 1.2 delta g). Insulin partly improved the ATP decrease in the subendocardium of the left ventricle of the diabetic hearts (from 3.5 to 10.2 mumol/g dry weight) but did not affect non-diabetic hearts (from 6.9 to 6.8 mumol/g dry weight). Insulin also partly improved the creatine phosphate decrease and the inorganic phosphate increase in diabetic hearts only. Lactate accumulation was greater in non-diabetic than in diabetic hearts, even in the presence of insulin (77 vs. 45 mumol/g dry weight). The results indicate that acute intracoronary application of insulin in diabetic hearts improves hypoperfusion with norepinephrine injury to a level above that of non-diabetic hearts, but does not improve a less severe injury in non-diabetic hearts.

Cardiovascular effects of the crowns-of-thorns starfish ( Acanthaster planci ) venom were examined in rats. The crude venom extracted from the spines of A. planci caused systemic hypotension associated with an increase in heart rate and a decrease in renal cortical blood flow when given i.v. The hypotensive effect of the venom was not inhibited by pretreatment with atropine, indomethacin or aprotinin, but was significantly inhibited by SRI 63–441, a platelet activating factor (PAF) antagonist. The venom caused dose-dependent vasorelaxation of the isolated rat aortic ring preparation precontracted by noradrenaline, an effect which was significantly attenuated by pretreatment with SRI 63–441, methylene blue or parabromophenacyl bromide. Denudation of the endothelium also diminished the vasorelaxing effect of the venom. Both the vasorelaxing and the hypotensive effects showed tachyphylaxis. These results suggest the release of PAF or a PAF-like substance from the endothelium by the venom.

Effects of bufadienolides such as bufalin (BF) and cinobufagin (CB), the main components of Senso (Ch'an Su), on myocardial Na+,K(+)-ATPase activity, the cardiotonic activity in vivo and the action potential of isolated guinea pig papillary muscle cells were compared with those of other cardiotonic drugs. 1) The rank order of potency for inhibition of myocardial Na+,K(+)-ATPase activity was BF greater than digoxin (DG) greater than digitoxin (DT) greater than telocinobufagin greater than gamabufotalin greater than cinobufotalin greater than CB greater than g-strophanthin (GS) greater than digitoxigenin (DTG) greater than resibufogenin (RB) when compared at the 50% inhibitory concentration. 2) In isolated papillary muscle cells, CB shortened the action potential duration (APD) dose-dependently. The order of potency for shortening of APD was GS greater than CB greater than DTG much greater than DT. 3) In open-chest guinea pigs, intraduodenal administration of BF or CB increased the myocardial contractile force (MCF), but did not affect the heart rate. The order of potency for increase in MCF was as follows: methyldigoxin, proscillaridin greater than BF greater than CB greater than DG greater than Senso much greater than DT, DTG, RB. These results indicate that CB has a shortening effect on APD and an inhibitory effect on Na+,K(+)-ATPase activity along with its cardiotonic effect, like GS.

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.

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. Keywords:: tetrahydrobiopterin, 2,4-diamino-6-hydroxypyrimidine, endothelial function, acetylcholine, sodium nitroprusside

SUMMARY 1. β-Adrenoceptor blocking activities of nipradilol, its four optical isomers (RR, RS, SR, SS) and denitro nipradilol were evaluated using pig isolated coronary arteries. 2. (–)-Isoprenaline produced concentration-dependent relaxations of the arteries, which were antagonized by nipradilol, its four optical isomers or denitro nipradilol under KCl-induced contracture. 3. The order of pA2 values for β-adrenoceptor blocking activities was SR > nipradilol > SS ≥ denitro nipradilol > RR > RS. 4. The nitroxy group in nipradilol appears to enhance its β-adrenoceptor blocking activity, because the β-adrenoceptor blocking activity of nipradilol was more potent than that of denitro nipradilol. 5. Isomers that have the S configuration (SR, SS) at the 2′ position (having a hydroxyl group) in the aryloxypropanolamine showed more potent β-adrenoceptor blocking activity than isomers that have the R configuration (RR, RS). 6. Isomers that have the R configuration (SR, RR) at the 3 position (having a nitroxy group) in the benzopyran ring showed more potent β-adrenoceptor blocking activity than those with the S configuration (SS, RS). 7. It is suggested that the difference in configuration of the chemical structure of nipradilol may result in variations of binding affinity for the β-adrenoceptor.

We studied the use of high-performance liquid chromatography (HPLC) with spectrofluorometric detection, using a solid-phase extraction for a simple, rapid and sensitive determination of plasma carvedilol levels in rats. Extracted aliquots were analyzed by HPLC, using a reversed-phase octadecyl silica column. The analytical mean recovery of carvedilol added to the blank plasma was 94.2%. The detection limit was 3.6 ng/ml in the plasma. The reproducibilities (C.V.) were 2.7-7.5% for the within-day assay, and 2.6-7.4% for the between-day assay, indicating that the method was effective for the determination of carvedilol plasma levels.

1. Effects of plancinin, a new anticoagulant peptide, on the human blood coagulation cascade were investigated. 2. Plancinin prolonged both activated partial thromboplastin time and prothrombin time, and it significantly inhibited factor X activation by both intrinsic (factor IXa–factor VIIIa–phospholipids–Ca 2+ ) and extrinsic (factor VIIa–tissue factor–phospholipids–Ca 2+ ) tenase complexes and prothrombin activation by prothrombinase complex (factor Xa–factor Va–phospholipids–Ca 2+ ) to 13.8%, 4.8% and 10.5% of control value, respectively. 3. Results indicate that sites of anticoagulant action of plancinin may be located in activation steps of prothrombin and factor X.

To clarify the hypothesis that organic nitrates are converted to nitric oxide (NO) via nitrite ion (NO2−) by glutathione S-transferase, the metabolic conversion of four nitrates was examined in pig coronary arteries and compared with that in rat liver. Nitrates caused the relaxation of the artery muscles with the order of nitroglycerin > isosorbide dinitrate > nicorandil ≧ nipradilol, whereas the order of NO formation in the arteries was nitroglycerin > isosorbide dinitrate > nipradilol > nicorandil. The same order of NO formation from the nitrates was also observed in liver cytosol. Nicorandil may cause more relaxation than nipradilol by both NO releasing and other (unknown) actions. Although the order of the potency in NO2− formation from the nitrates in liver cytosol was the same as that seen in NO formation, NO2− was not detected in pig coronary arteries. Thus NO2− formation from the nitrates correlated with NO formation in liver cytosol but not in pig arteries. When nonenzymatic and enzymatic NO formations from nitroglycerin were examined in the arteries, the enzymatic NO formation, which was not inhibited by glutathione S-transferase inhibitors, was 13% of the total NO. These results indicate that in pig coronary arteries, nitrates release NO mostly through a nonenzymatic manner, although there is a slight amount of enzymatically produced NO, and glutathione S-transferase may not contribute to the enzymatic NO formation.

The antioxidative effects of beta-adrenoceptor antagonists and related compounds were investigated. Among the beta-adrenoceptor antagonists, the agents with a potent membrane-stabilizing activity such as bopindolol and propranolol strongly inhibited the hydrogen peroxide (H2O2)-induced lipid peroxidation of liver microsomes. Fifty percent inhibition concentration values for the lipid peroxidation of bopindolol, 18-502 (metabolite of bopindolol) and propranolol were calculated to be 1.8 microM, 10 microM and 2.3 microM, respectively. The same potency order of the agents for the inhibition of lipid peroxidation was observed in rat heart homogenates. Furthermore, cytochrome P-450-catalyzing lipid peroxidation in microsomes and H2O2-induced lipid peroxidation in coronary arteries or cardiac muscles of pigs were also inhibited by bopindolol, whereas propranolol was less effective. Bopindolol and 18-502, but not propranolol, scavenged a stable free radical 1,1-diphenyl-2-picrylhydrazyl. Thus it was concluded that bopindolol that has membrane-stabilizing and radical scavenging activities is a more potent antioxidant than propranolol and may produce a beneficial effect for the treatment of ischemic cardiac diseases.

This study was designed to examine haemodynamic and haematologic effects of the crown-of-thorns starfish venom ( Acanthaster planci venom: APV) in dogs. Severe systemic hypotension, thrombocytopenia and leukopenia were induced by APV (1.0 mg protein/kg i.v.), followed by gradual return to the baseline level within 60 min. Hypotension was presumably caused by two factors: an early decrease in systemic vascular resistance and the large reduction in cardiac output due to reduced ventricular filling. Indomethacin, a cyclooxygenase inhibitor, remarkably suppressed systemic hypotension induced by APV. The peak reduction in systemic pressure was associated with concomitant rise of plasma 6-keto-PGF 1α , a major stable metabolite of prostacyclin. Thus, the hypotensive effect of APV may be caused primarily by prostacyclin and/or some vasodilating prostaglandins. In contrast, thrombocytopenia and leukopenia were not affected by cyclooxygenase inhibitor, 5-lipoxygenase inhibitor or platelet activating factor (PAF) receptor antagonist. When APV was administered repeatedly, tachyphylaxis was developed in haemodynamic effects, but not in haematologic effects. These findings suggest that APV-induced hypotensive effects may occur mainly through endogenous production of vasodilating prostaglandins including prostacyclin, although APV-induced thrombocytopenia and leukopenia may be caused by other mechanism(s) unrelated to arachidonate metabolites and/or PAF.

1. Cumulative administrations of U46619, a thromboxane A 2 analogue, and prostaglandin (PG) F 2α produced concentration-dependent contractions of isolated dog renal arterial preparations, which were significantly and concentration-dependently inhibited by vapiprost. 2. A bolus administration of U46619 or PGF 2α produced sustained contracture of these preparations, which was concentration-dependently relaxed by cumulative vapiprost. 3. Results indicate that vapiprost inhibits U46619- and PGF 2α -induced dog renal arterial contractions through antagonism for so-called TP receptors.

Regional vascular responses to the thromboxane A2 analogue U46619 and effects of the selective thromboxane receptor blocking drug vapiprost on these responses were examined in anesthetized dogs. Hemodynamic responses to U46619 (0.5 micrograms/kg into the left atrium), norepinephrine (NE, 0.3 microgram/kg, i.v.) and angiotensin II (AII, 30 or 60 ng/kg, i.v.) were periodically tested before and after administration of vapiprost (10, 30 or 100 micrograms/kg, i.v.) or its vehicle. In the absence of vapiprost, U46619 increased total peripheral (TPR), vertebral (VR), coronary (CR) and renal (RR) vascular resistance by 60.1 +/- 4.7%, 33.6 +/- 4.9%, 15.3 +/- 1.3% and 120.8 +/- 17.4%, respectively, indicating that vasoconstrictor responses to U46619 were most prominent in the renal vascular bed as compared to those in the vertebral or coronary vasculatures. Vapiprost as well as the vehicle did not affect the base-line hemodynamics. However, vapiprost apparently inhibited the U46619-induced vasoconstriction in all measured vascular beds in a dose-related manner without attenuating vasoconstrictor responses to NE compared to the inhibitions of VR and CR. These results demonstrate that there was a regional difference both in the vasoconstrictor responses to U46619 and in the blocking effects of vapiprost, and indicate that vapiprost is a potent and selective antagonist for thromboxane receptors in vivo.

The relationship of myocardial high-energy phosphate depletion and lactate accumulation with contractile dysfunctions was investigated in streptozotocin-diabetic (DM) and normal rat hearts. The isolated hearts were perfused with 10 −6 m norepinephrine (NE) at various low-flow rates (0.4–6 ml/min/g heart wt) for 1 h. Left ventricular pressure (LVP) and contractile force (CF) were monitored, through a water-filled balloon in LV and through a hook attached to the apex, respectively. In DM hearts resting CF (diastolic tension) increased, when the perfusion flow rate was reduced below 6 ml and reached a maximum at a flow rate of less than 3 ml. The large increase in LV stiffness correlated with an elevation in diastolic LVP. In normal hearts these parameters were elevated at a flow rate below 1 ml. A flow-dependent decrease in developed CF was more prominent in DM than in normal hearts, while developed LVP and perfusion pressure were slightly higher in DM hearts with a marked increase in the LV stiffness. A flow-dependent decrease in high-energy phosphates and increases in inorganic phosphate and lactate were more prominent in the inner than in the outer layer of LV free wall in both groups. The change of ATP in the inner layer was greater, while increases of lactate in both layers were smaller in DM hearts. Changes in mechanical parameters correlated well with the ATP decrease and lactate increase in the inner layer in both groups. The correlation curves, however, were not coincidental: at the same low ATP and high lactate level, the LV stiffness was higher in DM hearts. Results indicate that DM hearts are more susceptible to flow-reduction with NE and depletion of total ATP in their tissue, and easily suffer from increased LV stiffness. This cannot be explained by the rate of decrease in total ATP and lactate accumulation alone.

1. 1. Nipradilol produced concentration-dependent relaxations of isolated rat aorta ring preparations under the contracture induced by norepinephrine or KCl, which were not significantly influenced by the previous incubation with nipradilol but significantly depressed by methylene blue. 2. 2. The previous incubation with nipradilol did not influence the relaxant responses to nitroglycerin. 3. 3. Five different methods for measurement of vascular glutathione content did not give the satisfiable results on the detected value of glutathione content in isolated rat aorta tissues. 4. 4. Results indicate that nipradilol will not develop the tolerance to nipradilol itself and nitroglycerin.

1. 1. Inhibition of sodium(Na + ), potassium(K + )-ATPase activity was dependent on the concentration of ouabain and inverse to the concentration of potassium ([K + ]) in the reaction mixture. 2. 2. Contractility of isolated rat aorta preparation in response to norepinephrine was augmented by ouabain and low [K + ]. 3. 3. Results suggest that inhibition of Na + ,K + -ATPase activity will be correlated with augmentation of vascular contractility maybe through activation of Na + -calcium exchange system.

1. 1. Nitroglycerin caused dose-dependent increases in regional myocardial contractile force (MCF) in open-chest dogs, along with dose-dependent decreases in left ventricular end-diastolic (LVEDP) and arterial pressures and an increase in plasma catecholamines level. 2. 2. The increase in MCF could not be completely prevented by propranolol along with a slight decrease in LVEDP and no increase in heart rate, although a nifedipine-produced increase in MCF without a significant decrease in LVEDP disappeared with propranolol despite the same decrease in arterial pressure.

Effects of insulin on contractile and energy metabolic dysfunctions during hypoperfusion (2 ml/min/g heart wt., 60 min) with 10(-6) M norepinephrine were studied in paced hearts isolated from streptozotocin-diabetic rats. Insulin (2 mU/min/g heart wt.) was infused 20 min before and during hypoperfusion (pre-treated group) or 30 min after the onset of hypoperfusion (post-treated group). Hearts in the non-treated group were hypoperfused without insulin and other hearts in the control group were not hypoperfused. In the non-treated group, resting contractile force (CF) and resting left ventricular pressure (LVP) were significantly elevated to maximum levels within 30 min after hypoperfusion and these elevations were restored in the pre-treated group but not in the post-treated group. Developed CF was depressed in the non-treated group and improved significantly in the pretreated group but not in the post-treated group. Developed LVP was depressed in the non-treated group, and depression was slightly larger in the pre-treated group. In the non-treated group, ATP and creatine phosphate contents in the left ventricle significantly decreased. Decreases in ATP and creatine phosphate contents in the inner layer were partially restored in the pre-treated group but not in the post-treated group. Lactate significantly increased in the non-treated group and increased even further in the insulin treated groups. These results indicate that contractile dysfunction during hypoperfusion with norepinephrine is improved by pre-treated insulin, as is partial recovery of energy metabolism.

Characteristics of the cardiovascular effects of habu venom were studied in vivo and in vitro in rats. Aortic pressure (AoP), heart rate (HR) and renal cortical blood flow (RCBF) assessed by a laser-Doppler flowmeter were measured in anesthetized rats. Administration of habu venom (0.2-1.6 mg/kg, i.v.) dose-dependently produced a fall in AoP without a marked change in HR. RCBF decreased significantly along with the decline in AoP. Heated habu venom (70 degrees C for 5 min) or the residual venom by dialysis produced similar hemodynamic responses to nonheated crude habu venom. Although habu antivenin significantly reduced the effects of habu venom, indomethacin, aprotinin, atropine, captopril and chlorpheniramine did not. Methylprednisolone significantly attenuated these effects. Habu venom (10(-5) to 3 x 10(-4) g/ml) produced dose-dependent relaxations of the isolated rat aorta preparations precontracted with norepinephrine or KCl, which were not affected by indomethacin, nordihydroguaiaretic acid, p-bromophenacyl bromide, mepacrine, methylene blue or de-endothelialization. These results indicate that habu venom, particularly its heat-stable component(s) which has at least more than 10,000 molecular weight, produces hypotensive and vasorelaxant effects in rats, and suggest that eicosanoids, kinins, histamine, ACh, and endothelium are scarcely involved in these effects.