The antinephritic effect of DP-1904 [6-(1-imidazolylmethyl)-5, 6, 7, 8-tetrahydronaphthalene-2-carboxylic acid hydrochloride], a thromboxane (TX) A₂ synthase inhibitor, was compared with that of OKY-046 and azathioprine, using an experimental model of nephritis, crescentic-type anti-glomerular basement membrane (GBM) nephritis. Test drugs were given p.o. once daily from an autologous phase in which proteinuria was already fully developed. DP-1904 (15 and 45 mg/kg per day) and OKY-046 (20 mg/kg per day), another TXA₂ synthase inhibitor, significantly inhibited the development of glomerular alteration as well as the elevation of proteinuria. On the other hand, azathioprine (20 mg/kg per day), an immunosuppressive agent, failed to suppress the proteinuria. A single administration of DP-1904 or OKY-046 inhibited glomerular TXB₂ production and increased glomerular prostaglandin (PG) E₂ and 6-keto PGF_1α production in nephritic rats. Both drugs apparently decreased the depositions of both rabbit immunoglobulin (Ig) G and rat IgG on GBM in nephritic rats, but azathioprine inhibited only the deposition of rat IgG. These results suggest that DP-1904 may be an effective agent for the treatment of proliferative glomerulonephritis and its antinephritic effect may be due to the amelioration of abnormal metabolism of arachidonic acid.

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The effects of potassium channel openers NIP-121 ((+)-7, 8-dihydro-6, 6-dimethyl-7-hydroxy-8-(2-oxo-piperidine-1-yl)-6H-pyrano[2, 3-f]benz-2, 1, 3-oxadiazole) and levcromakalim were examined in vitro and in vivo. In isolated canine vascular beds, NIP-121 (3 × 10^-9 to 10^-7 M) and levcromakalim (3 × 10^-8 to 10^-6 M) produced a concentration-dependent reduction in the vasoconstrictor responses to U46619. The effects were antagonized by glibenclamide, an ATP-sensitive potassium channel blocker. The maximal relaxation was more than 70% of the maximal vasodilation induced by papaverine (10^-4M), except in the basilar artery. These compounds had very potent effects on the coronary and cranial mesenteric arteries and saphenous vein. In the coronary perfused rat heart, both compounds (10^-7 M) also increased coronary perfusion flow. The effects were also inhibited by glibenclamide (10^-6 M). In anesthetized dogs, NIP-121 (1 to 10 μg/kg (3.2 to 32 nmol/kg), i.v.) and levcromakalim (3 to 30 μg/kg (10.5 to 105 nmol/kg), i.v.) dose-dependently increased coronary and renal blood flow. NIP-121 and levcromakalim at higher doses produced the greatest increase in coronary blood flow among the blood vessels examined, in spite of the hypotensive effect. In conclusion, NIP-121 and levcromakalim were similarly selective vasodilators on the canine isolated coronary and cranial mesenteric arteries and saphenous vein, and they selectively increased coronary blood flow in vivo. With respect to increasing the coronary blood flow, NIP-121 had a fourfold greater potency than levcromakalim. This effect might be related to the glibenclamide-sensitive potassium channels.

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The effects of stable strontium were investigated in ovariectomized (OVX) rats by calcium balance and calcium kinetic studies, histomorphometric analysis and measurements of calcium levels in bone. After 10 days of pair-feeding with a control diet, 71-day-old female Wistar rats were either shamoperated (Sham group) or ovariectomized. The OVX rats were divided into two subgroups: those that were treated with strontium (OVX+Sr group, strontium intake; 87.5 μmol/day/rat) and those that were not (OVX group). Both groups were pair-fed their respective control or strontium diets for 2 weeks. Calcein and tetracycline were injected every 2 weeks from 1 week before ovariectomy to calculate the rate of bone formation in the diaphyseal femora cortex (% BFFC). In the OVX group, urinary calcium and % BFFC decreased, while bone resorption, bone formation and femora length increased at the end of the experiment, as compared with those in the Sham group. No such changes were observed in rats in the OVX+Sr group. The calcium balance, calcium levels in bone and trabecular bone volume in the metaphysis did not change in any of the three groups. These results suggest that strontium may be able to prevent the changes in bone turnover induced by estrogen deficiency.

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FRG-8813 ((±)-2-(furfurylsulfinyl)-N-[4-[4-(piperidinomethyl)-2-pyridyl]oxy-(Z)-2-butenyl]acetamide) is a novel histamine H₂-receptor antagonist with gastric antisecretory and gastroprotective activities. The present study was designed to investigate the property of gastroprotective action. The oral ED₅₀ values for inhibition of mucosal lesions against 1% NH₃-, 60% ethanol in 0.15 N HCl-, 100% ethanol-, 0.6 N HCl- and sodium taurocholate in 0.4 N HCl-induced damage were 3.3, 11.1, 14.9, 23.3 and 23.1 mg/kg, respectively. FRG-8813 was gastroprotective despite pretreatment with omeprazole, suggesting that the protective effect is independent of its antisecretory activity. It is unlikely that FRG-8813 works as a mild irritant because it showed a gastroprotective effect after intraperitoneal injection, but oral administration itself did not influence the rat gastric mucosa. Although pretreatment with indomethacin or N-ethylmaleimide did not affect the gastroprotection of FRG-8813, chemical deafferentation induced by capsaicin abolished the gastroprotection. Furthermore, prior administration of tetrodotoxin, the calcitonin generelated peptide (CGRP) antagonist hCGRP_8-37 or N^G-nitro-L-arginine attenuated the gastroprotection of FRG-8813 as well as that of capsaicin. In contrast to capsaicin, repeated administration of FRG-8813 neither enhanced the susceptibility of the mucosa to damage nor affected the gastroprotective action of short-term treatment. In conclusion, these results suggest that FRG-8813 has gastroprotective activity independently of acid antisecretory activity and that capsaicin-sensitive nerves may be partially or fully involved in the gastroprotective mechanisms of FRG-8813.

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Electrophysiological effects of sematilide, a novel class III antiarrhythmic agent, were examined and compared with those of (±)sotalol in guinea pig left atrium by a conventional microelectrode technique. Application of 0.1-1000 μM sematilide or 1-1000 μM (±)sotalol concentration-dependently prolonged the duration of action potentials (APD) that were elicited by electrical stimulation at 1 Hz. Other parameters of action potentials such as the maximum upstroke velocity of phase 0 depolarization, action potential amplitude and resting membrane potential were not affected significantly by these drugs in the concentration ranges employed. The prolongation of APD by sematilide or (±)sotalol was accompanied by a corresponding increase in the effective refractory period (ERP). Approximately a 30% increase in ERP was obtained by the treatment with 5 μM sematilide or 100 μM (± )sotalol, suggesting that sematilide as a class III antiarrhythmic agent is approximately 20 times more potent than (±)sotalol on a molecular basis. When the stimulation rate was increased stepwise from 0.2 to 2 Hz, the relative increase in APD at 90% repolarization by the treatment with sematilide and (±)sotalol was slightly larger at 2 Hz than at 0.2 Hz, indicating that “reverse rate-dependence” was not observed under these conditions. These results may suggest a possibility that sematilide effectively blocks atrial arrhythmia.

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Nitric oxide released from vascular endothelium plays important regulatory roles in cardiovascular and pulmonary systems. Epidemiological studies suggest that diesel exhaust particles (DEP) seem to be one of the causative factors responsible for the recent increase in pulmonary diseases. To clarify the pathogenic mechanism, the effects of DEP on vascular endothelial functions were investigated in terms of endothelium-dependent relaxation. Ring preparations of rat thoracic aorta were preincubated for 10 min with a DEP suspension (1, 10, 100 μg/ml) at 37°C in organ baths and relaxed with cumulative additions of acetylcholine following precontraction with phenylephrine (10^-6 M). The relaxation was attenuated by DEP-exposure in a concentration-dependent manner. An addition of superoxide dismutase (SOD) completely abolished the inhibitory effect of DEP at lower concentrations, but only partially at the higher concentration. DEP (10 μg/ml) neither affected the contractile response to phenylephrine in intact aortic rings nor the endothelium-independent relaxation by sodium nitroprusside in denuded rings, while DEP (100 μg/ml) significantly attenuated both responses. These results suggest that 1) inhaled DEP causes pulmonary inflammation by inhibiting the endothelial formation and/or the effect of nitric oxide and 2) SOD reduces the adverse effects.

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The in vitro potencies of a novel inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT), E5324 (n-butyl-N''-[2-[3-(5-ethyl-4-phenyl-1H-imidazol-1-yl)propoxy]-6-methylphenyl]urea), were studied. E5324 was found to be a potent ACAT inhibitor in microsomes from a various tissues and in cultured cell homogenate, with IC₅₀ values in the range of 0.044 to 0.19 μM. The kinetic study on E5324 showed that the inhibition of rat intestine ACAT was competitive with respect to oleoyl CoA. E5324 inhibited [³H]oleate incorporation into cholesteryl [³H]oleate in phorbol ester-treated THP-1 cell lines (IC₅₀=0.44 tμM). The rate of [³H]oleate incorporation into phospholipids and triglycerides was not affected by E5324. In an experiment with [³H]cholesterol as the substrate for ACAT, E5324 also inhibited [³H]cholesteryl ester synthesis (IC₅₀=0.41 μM). Furthermore, E5324 prevented accumulation of both esterified and total cholesterol in acetyl low density lipoprotein-loaded THP-1 cells. These results indicate that E5324 is a potent and selective ACAT inhibitor and prevents cholesteryl ester accumulation in macrophages.

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In this study, we investigated the effects of KBT-3022 (ethyl 2-[4, 5-bis(4-methoxyphenyl)-thiazol-2-yl]pyrrol-1-ylacetate), a potent and long-lasting anti-platelet agent, in several experimental thrombosis models and compared them with those of other anti-platelet drugs. Oral administration of KBT-3022 prevented arachidonic acid-induced death due to pulmonary embolism in mice and rabbits with respective ED₅₀ values of 0.29 and 0.12 mg/kg. The protective effect of acetylsalicylic acid (ASA) against mortality was weaker than that of KBT-3022, and ticlopidine hydrochloride (TP) showed no such effect in these models. In a guinea pig arterio-venous shunt model, the inhibition by KBT-3022 of thrombus formation on a silk thread inserted into the shunt was dose-dependent and 300 and 30 times more potent than the inhibition obtained with ASA and indomethacin, respectively. In a model of aortic thrombosis induced by perivascular application of 20% silver nitrate solution, KBT-3022 (1 mg/kg, p.o.) inhibited thrombus formation significantly, ASA (100 mg/kg, p.o.) tended to inhibit it, and TP had no effect. However, in a stasisinduced venous thrombosis model in guinea pigs, TP inhibited thrombus formation significantly, but KBT-3022 and ASA were ineffective. These results suggest that KBT-3022 may be a useful drug for the treatment and/or prophylaxis of thrombus formation in shunts and aortic thrombosis.

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Since the development of tolerance to morphine antinociception in formalin-treated mice was delayed and diazepam normalized the delay, the involvement of GABAergic systems in the process was investigated. Gamma amino-an-butyric acid (GABA) at 10 mg/kg and the GABA_A-receptor agonist muscimol at 0.05 mg/kg, i.p., 30 min before daily morphine injection at 10 mg/kg, s.c. completely reversed the delay in the development of morphine tolerance in the formalin-treated mice. The GABA_A antagonist bicuculline at 1 mg/kg and the Cl^--channel blocker picrotoxin at 1 mg/kg extinguished the reverse effect of muscimol and GABA, respectively. In contrast, the GABA_B antagonist CGP 35348 (3-aminopropane-diethoxymethyl-phosphinic acid) up to 100 mg/kg, i.p. failed to abolish the GABA effect; and baclofen, a GABA_B-receptor agonist, at 0.5 and 2 mg/kg, i.p., 30 min before morphine was without effect on the delay. On the other hand, bicuculline was incapable of abolishing the reverse effects of diazepam on the delay of tolerance development; and likewise, the reverse effect of muscimol was not affected by flumazenil. No appreciable influence of these GABA-related compounds was seen on morphine antinociception itself nor the development of tolerance in normal mice. These results suggest that the benzodiazepine-GABA_A-Cl^- channel complex is involved in the mechanism underlying the delay of the development of morphine tolerance in formalin-treated mice; however, it is deduced that benzodiazepine-receptor and GABAergic systems are not always functionally coupled to each other in the mechanisms.

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We investigated the effects of KW-3902 (8-(noradamantan-3-yl)-1, 3-dipropylxanthine), a potent adenosine A₁-receptor antagonist, on the nephrotic edema induced by puromycin aminonucleoside (PAN; 100 mg/kg, i.v.) in rats. The treatment with PAN decreased urine volume and urinary excretions of sodium and potassium, resulting in the ascites formation in 7 days. In rats with the nephrosis, KW-3902 (0.01-1 mg/kg/day for 3 days, p.o.) showed diuretic effects and reduced the volume of ascites, as was the case with furosemide (30 mg/kg/day) and trichlormethiazide (1 mg/kg/day). These results suggest that even in the nephrotic state, the adenosine A₁-receptor antagonist can be an effective diuretic to ameliorate edema.

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Effects of arginine-vasopressin (AVP) on the contractile force, action potential (AP) and intracellular pH (pH_i) were studied in isolated guinea pig papillary muscles using conventional and ionselective microelectrode techniques. AVP increased the developed tension and the resting tension, and these responses were attenuated by the V₁-receptor antagonist OPC-21268 (1-{1-[4-(3-acetylaminopropoxy)benzoyl]-4-piperidyl}-3, 4-dihydro-2(1H)-quinolinone). However, AVP failed to affect AP configuration or pH_i. These results suggest that AVP produces a positive inotropy by mechanism(s) other than intracellular alkalinization.

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We investigated the effects of microtubule inhibitors, taxol and colchicine, on the axonal branching and elongation in cultured rat hippocampal neurons. Taxol (50 nM) did not affect the morphology of neurons cultured under the control conditions, but significantly reduced the axonal branching stimulated by basic fibroblast growth factor. The axonal elongation stimulated by astrocyte-conditioned medium was not affected by the same concentration of taxol. Colchicine (10 nM) showed similar effects as taxol. These results suggest that microtubules play more important roles in axonal branching than in axonal elongation.

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We reported that centrally applied bombesin probably excites both the gastric sympathetic and adrenomedullary systems and thus induces inhibition of gastric acid secretion. In the present study, therefore, we examined whether or not centrally applied bombesin directly affects sympathetic nerve activities in rats anesthetized with urethane. Intracerebroventricular administration of bombesin (0.3 and 3.0 nmol) increased discharge rates of the sympathetic branch as well as those of the adrenal branch of preganglionic greater splanchnic nerves. These effects were not secondary to changes in arterial blood pressure by bombesin. In conclusion, centrally applied bombesin directly activates both the sympathetic and adrenomedullary systems.

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The aim of this study was to characterize injuries of LLC-PK₁ and MDCK cells exposed to hypoxia and reoxygenation. Exposure of LLC-PK₁ cells to hypoxia reduced the ATP contents and increased the leakage of lactate dehydrogenase (LDH), but MDCK cells had no such injuries. Hypoxia-reoxygenation of LLC-PK₁ cells dramatically increased LDH leakage, which was suppressed by free radical scavengers, N, N'' diphenyl p-phenylenediamine, superoxide dismutase and N, N'' dimethylthiourea. These results suggest that use of LLC-PK₁ cells has advantages for the investigation of ischemia-reperfusion injury of the kidney as an in vitro model and that generation of oxygen radicals is involved in the cellular injury induced by hypoxia-reoxygenation.

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