To examine the influence of amikacin-induced acute renal damage on the urinary excretion of furosemide and the time-dependent variation in the urinary amount of the agent, amikacin (1.2 g/kg) was given intraperitoneally to Wistar rats. Study I: Three percent b.w. of 1% NaCl solution was given orally before and after amikacin treatment, and an 8-hour urine for N-acetyl-β-D-glucosaminidase (NAG) was collected. Study II: Furosemide (30 mg/kg) in 3% b.w. of 1% NaCl solution was given orally at 12 a.m. or 12 p.m. before and after amikacin treatment, and an 8-hour urine for sodium and furosemide was collected. Following amikacin treatment, urinary excretion of NAG increased, while urine volume and urinary excretion of sodium and furosemide decreased. Urinary excretion of furosemide and its diuretic effects were significantly greater at 12 a.m. than at 12 p.m. before and after treatment. However the time-dependent differences in these parameters were diminished by amikacin treatment. These results suggest that the urinary excretion of furosemide is reduced and the extents of the time-dependent variation in the urinary furosemide and its diuretic effects are altered in rats with amikacin-induced renal damage.

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The properties of triphenyltin (TPT) in increasing intracellular Ca²⁺ ([Ca²⁺]_i) of thymocytes was studied, in comparison with those of A23187, by the use of fluorescent dyes to monitor membrane potential and [Ca²⁺]_i. Both 1 μM TPT and 30 nM A23187 increased the [Ca²⁺]_i associated with the hyperpolarization mediated by Ca²⁺-dependent K⁺ conductance. The time course for the TPT-induced increase in the [Ca²⁺]_i was much slower than that of A23187. When the external Ca²⁺ ([Ca²⁺]_o) was removed, TPT produced a slight, but persistent, increase in the [Ca²⁺]_i while A23187 caused only a transient increase in the [Ca²⁺]_i. Reintroduction of Ca²⁺ to the external solution produced an increase in [Ca²⁺]_i in both cases. Therefore, these results suggested that the increase in the [Ca²⁺]_i of thymocytes induced by TPT and A23187 was dependent on the presence of [Ca²⁺]_o and an intracellular Ca store. The potency of TPT in increasing the [Ca²⁺]_i was greater than those of diphenyltin and monophenyltin, suggesting an involvement of the lipophilic property of organotins in increasing [Ca²⁺]_i. The TPT-induced increase in the [Ca²⁺]_i may be partly responsible for the toxicity of TPT on organs and/or organ systems.

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In the rabbit isolated thoracic aorta, WB 4101 and 5-methylurapidil dose-dependently shifted the concentration-response curves for norepinephrine to the right. Schild plots showed that the inhibition of responses for WB 4101 and 5-methylurapidil was biphasic, implying that norepinephrine acted through two receptor populations. Clonidine produced a concentration-dependent contraction in the isolated rabbit thoracic aorta. WB 4101 and 5-methylurapidil antagonized the contractions for clonidine, and the Schild plot to both antagonists against clonidine yielded a monophasic slope. Schild plots of the results obtained from the inhibition by WB 4101 and 5-methylurapidil for norepinephrine in strips pretreated with chloroethylclonidine yielded a straight line with a slope of unity. Specific binding of [³H]prazosin in the aortic membrane preparations was saturable. The Hill coefficient obtained from the inhibition curves for clonidine was significantly different from unity. Clonidine interacted with two binding sites labelled by [³H]prazosin, but the low affinity site was completely eliminated by pretreatment with 10 μM chloroethylclonidine. These results suggest that the subtype activated by norepinephrine is different from that activated by clonidine, and that norepinephrine-induced contraction through both α_1A- and α_1B-subtypes and clonidine through only the α_1A-subtype in the rabbit thoracic aorta.

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The relationship between histamine (Hi)-induced depolarization and the cyclic AMP system in adipocytes was studied in guinea pigs, which seem to be more sensitive than rats to Hi. Hi caused a dose-dependent depolarization in guinea pig mesenterial and epididymal adipocytes with EC₅₀ values of 1.69 × 10^-7 M and 1.19 × 10^-7 M, respectively. Guinea pig adipocytes were 280-750 times more sensitive than rat adipocytes to Hi. Isoproterenol, forskolin and 3-isobutyl-1-methylxanthine (IBMX) also caused a depolarization, and the slopes of the concentration response lines for these drugs were almost the same as that for Hi. Furthermore, pretreatment with these drugs resulted in a potentiation of Hi-induced depolarization at lower concentrations which are not effective when each drug is used alone. In addition, Hi-induced depolarization was inhibited by pretreatment with prostaglandin E₁ (PGE₁) and insulin dose-dependently. The content of cyclic AMP in adipocytes was increased by Hi (10^-7 M) in association with a decrease in membrane potential. KT5720, a protein kinase A inhibitor, which provides no significant effect even at a concentration of 10^-6 M, showed an antagonistic effect on Hi-induced depolarization.

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Effects of phellodendrine (OB-5) on crescentic-type anti-GBM nephritis in rats and the cell number of the various leukocyte subpopulations in the glomeruli of the nephritic rats were investigated. OB-5 at 25, 50 and 100 mg/kg/day, p.o. prevented the urinary protein excretion by the 19th day after i.v.-injection of anti-GBM serum. In the OB-5-treated rats, plasma cholesterol and creatinine contents were lower than those of the control rats throughout the 40-day experimental period. Histopathological observations demonstrated that OB-5 inhibited the incidence of crescent formation, adhesion and fibrinoid necrosis in the glomeruli by the 41st day. OB-5 did not affect the plasma antibody titer against rabbit gamma globulin. The increases in total leukocytes, macrophages, cytotoxic/suppressor T cells, la positive cells, and IL-2 receptor positive cells in the glomeruli in OB-5, 100 mg/kg-treated rats as well as those of the animals treated with azathioprine or cyclosporin A were lower than those of the anti-GBM nephritic control. These results indicate that OB-5 was effective in crescentic-type anti-GBM nephritis and the antinephritic mechanisms of this agent may be due to its ability to inhibit the proliferation or the migration of macrophages and cytotoxic T lymphocytes in the glomeruli.

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Antinociceptive actions and effects of intracerebroventricular (i.c.v.) dynorphin-(1-13) (DYN) on morphine (MOR) analgesia and acute tolerance were studied in male Sprague-Dawley rats. Antinociceptive effect against hind paw pressure was produced by 30 μg of DYN, but not by 0.5-10 μg. Acetic acid writhing was inhibited dose-dependently by DYN at the doses of 2-30 μg, and the order of potency of the anti-writhing effect was β-endorphin > MOR > DYN >> Met-enkephalin. The anti-writhing effect of DYN that was partially antagonized by naloxone at 10 mg/kg, s.c. in MOR tolerant rats was the same as that in MOR naive rats. The anti-writhing effect of i.c.v.-MOR was increased synergistically by DYN. Continuous s.c. (6 mg/kg/hr) and i.c.v. (7.5 μg/rat/hr) infusion of MOR produced antinociception against hind paw pressure, which reached maximum (MAX) and attenuated thereafter during MOR infusion for 6 hr. The attenuation of antinociception was also produced during MOR infusion combined with multiple i.c.v.-injection of DYN. The MAX and area under the anti-nociceptive curve during MOR infusion was not affected by multiple injection of DYN, i.e., no effect of i.c.v.-DYN on the development of acute MOR tolerance induced by s.c.- and i.c.v.-infusion was observed. In conclusion, the anti-writhing effect of i.c.v.-DYN might not be mediated via mu-receptors, although DYN increased the anti-writhing effect of i.c.v.-MOR synergistically and the development of acute tolerance to MOR (i.c.v., s.c.) was not affected by i.c.v.-DYN.

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Chemical mediators responsible for the antigen-induced contractions of isolated, passively sensitized human and guinea pig lung parenchymas and bronchi or tracheas were evaluated by several antagonists and enzyme inhibitors, with emphasis on the effects of the potent and selective peptide leukotriene (p-LT) antagonist MCI-826. All of these preparations showed long-lasting contractions in response to an antigen challenge which lasted for more than 60 min. In either the human lung parenchyma and bronchus or guinea pig lung parenchyma, pretreatment with 10^-6 g/ml (2.4 × 10^-6 M) MCI-826 significantly inhibited the late phase at 10 to 60 min after the challenge of the contraction following slight suppression of the early phase. The early phase contractions of these preparations were moderately antagonized by 10^-6 g/ml mepyramine, but the late phases were not influenced or even rather enhanced. The combination treatment of MCI-826 with mepyramine additionally and markedly inhibited both phases of these preparations. On the other hand, although mepyramine apparently inhibited the early phase of the guinea pig tracheal contraction but not the late phase, no synergistic inhibitions of the contraction were observed when it was combined with MCI-826. The p-LT antagonist FPL 55712, atropine and indomethacin at 10^-6 g/ml either slightly inhibited or enhanced the contractions of human lung parenchymas, guinea pig tracheas and lung parenchymas, but the effects were not significant. From these results, it should be emphasized that p-LTs largely contribute to induction of the anaphylactic contractions of human lung parenchymas as well as human bronchi and guinea pig lung parenchymas but not guinea pig tracheas.

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We investigated the in vivo antagonistic activity of ONO-1078 against peptide leukotrienes (LTs) in guinea pigs. ONO-1078, when administered p.o. (0.3-3 mg/kg), caused a dose-dependent reduction of LTC₄-, LTD₄- and LTE₄-induced bronchoconstriction, LTD₄-induced airway microvascular leakage and LTD₄-induced increase in cutaneous vascular permeability. When administered intravenously, ONO-1078 (3-30 μg/kg) inhibited these responses approximately 200-600 fold more potently than FPL55712. When guinea pigs were treated with indomethacin to examine the antagonism of ONO-1078 on the direct action against peptide LTs, intravenous (3-30 μg/kg) and oral (0.3-3 mg/kg) administration of ONO-1078 also inhibited LTC₄- and LTD₄-induced bronchoconstriction, and its activity was approximately 300-500 fold more potent than that of FPL55712. ONO-1078 (10 mg/kg, i.v.) had no inhibitory effect on bronchoconstrictions induced by histamine, acetylcholine, serotonin, arachidonic acid, LTB₄, prostaglandin (PG) F_2α, PGD₂, 9α, 11β-PGF₂, a stable thromboxane A₂ mimetic agent and platelet activating factor. Furthermore, oral administration of ONO-1078 (1-10 mg/kg) inhibited slow-reacting substance of anaphylaxis mediated bronchoconstriction induced by antigen in a dose-dependent manner. These results indicate that ONO-1078 is an extremely potent, selective and orally active peptide LT antagonist and that oral administration of ONO-1078 antagonizes not only exogenously administered peptide LTs but also endogenous peptide LTs.

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We evaluated the antagonist activity of ONO-1078 against peptide leukotrienes (LTs) by a radioligand binding assay and functional experiments in guinea pigs. In the radioligand binding assay, ONO-1078 inhibited [³H]LTD₄ and [³H]LTE₄ bindings to lung membranes (K_i = 0.99 and 0.63 nM, respectively) and was 2, 000- to 3, 000-fold more potent than FPL55712. Antagonism of ONO-1078 against [³H]LTC₄ binding (K_i = 5640 nM) was approximately twofold more potent than that of FPL55712. The antagonism of ONO-1078 against [³H]LTD₄ binding was competitive. In functional experiments, ONO-1078 showed competitive antagonism against the LTC₄- and LTD₄-induced contractions of guinea pig trachea and lung parenchymal strips with a pA₂ range of 7.70 to 10.71 and was approximately 400- to 3, 300-fold more potent than FPL55712. Interestingly, in the presence of an inhibitor of the bioconversion of LTC₄ to LTD₄, ONO-1078 also antagonized the LTC₄-induced contraction of guinea pig trachea (pA₂ = 7.78). ONO-1078 significantly reversed the LTD₄-induced prolonged contraction without effect on the KCl- and BaCl₂-induced contractions of guinea pig trachea. Furthermore, ONO-1078 antagonized the antigen-induced SRS-A mediated contraction of guinea pig trachea. On the other hand, ONO-1078 showed no antagonism against histamine, acetylcholine, 5-hydroxytryptamine, prostaglandin D₂ and U-46619. In addition, ONO-1078 showed little or no effect on the activities of cyclooxygenase, 5-lipoxygenase and thromboxane synthetase. These in vitro studies indicate that ONO-1078 is a highly potent, selective and competitive antagonist of peptide leukotrienes that acts with higher affinity at LTD₄ and LTE₄ receptors than LTC₄ receptors.

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The effects of ulinastatin (ULN), a human urinary protease inhibitor, on liver injury caused by ischemia-reperfusion were studied in rats. In the liver ischemia-reperfusion model, ULN suppressed the elevation of serum transaminase levels and tissue lipid peroxide levels in the liver. ULN did not exhibit a radical-trapping action on the superoxide and hydroxyl radicals as measured by electron spin resonance (ESR). ULN suppressed formylmethionyl-leucyl-phenylalanine (FMLP) and phorbol myristate acetate (PMA)-induced superoxide production from polymorphonuclear leukocytes (PMNs) as measured by the cytochrome c assay. ULN did not inhibit either xanthine oxidase (XO) activity or the conversion of xanthine dehydrogenase (XDH) to XO during the ischemic period. ULN also strong ly protected against the hypotonic hemolysis of rat erythrocytes. These results suggest that ULN''s membrane stabilizing action and suppressive effect against PMNs superoxide production might be attributed to its suppressive effect on the liver''s lipid peroxidation caused by ischemia-reperfusion.

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The influences of extracellular Ca²⁺ and Mg²⁺ concentrations on the basal secretion of glycoconjugates from rabbit trachea in organ culture were examined. Over 80% of the ³⁵S-labeled and [³H]glucosamine-labeled glycoconjugates secreted by the trachea were digested upon incubation with chondroitinase ABC. The basal secretion did not occur in the medium at 4°C, indicating an energy-dependent process. The basal secretion at 37°C of ³⁵S-labeled glycoconjugates was prominently suppressed in Mg²⁺-free Tyrode solution but not in Ca²⁺-free Tyrode solution containing ethyleneglycol bis(2-aminoethylether)tetraacetic acid (EGTA). In contrast, the basal secretion of [³H]glucosamine-labeled glycoconjugates was not affected by the Mg²⁺ concentration in the medium. The results suggest that extracellular Mg²⁺ largely contributes to sulfation of glycoconjugates basally secreted from rabbit trachea.

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Betaxolol is a new β-blocker that has been reported to have β₁-selectivity, and it is devoid of both membrane stabilizing action and intrinsic sympathomimetic action. The effects of betaxolol on systemic and regional hemodynamics were examined in conscious spontaneously hypertensive rats (SHR) by a microsphere method and compared with the effects of atenolol. A single oral administration of betaxolol at 1 and 10 mg/kg decreased the mean arterial pressure in a dose-dependent manner. At the same doses, atenolol also showed a similar but weak hypotensive effect. Both of these drugs at the high dose decreased cardiac output and heart rate and at the low dose, did not. Total peripheral resistance decreased by only betaxolol at the low dose. Betaxolol showed a tendency to normalize the hemodynamic abnormalities which were observed in the kidney, spleen and gastrointestinal tract of SHR, while atenolol did not. It should be noted that betaxolol increased the flow rate in the kidney, which may be explained by its direct vasodilatory action on renal blood vessels. In conclusion, betaxolol showed an antihypertensive action at the doses of 1 and 10 mg/kg, exhibited the characteristics of a β₁-blocker and produced preferable effects on regional hemodynamics in SHR.

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Location of stretch receptors triggering the peristalsis was investigated in the isolated guinea pig ileum. Peristalsis was cyclically induced by perfusing the lumen with Krebs solution flowing at a constant rate. Peristalsis was promptly abolished by serosally applied 3 × 10^-7 M tetrodotoxin, 10^-4 M lidocaine, 10^-6 M morphine or 10^-5 M nicotine, confirming the claim that peristalsis was neurally regulated by the myenteric plexus. Intraluminal application of 3 × 10^-7 M tetrodotoxin not only blocked the peristalsis, but also inhibited the contractions of the longitudinal muscle elicited by transmural stimulation or 10^-4 M nicotine by the same extent as those by serosal tetrodotoxin, suggesting that the blockade of peristalsis was due to the tetrodotoxin infiltrating into the muscle layer. In contrast, intraluminal application of 0.1% glutaraldehyde or perfusing the lumen with the low NaCl (20 mM)-containing Krebs solution abolished the peristalsis without critically inhibiting the neurogenic contractions of the longitudinal muscle, indicating that the blockade of peristalsis by these intraluminal treatments was ascribed to the actions on the mucosal layer. These results may imply that stretch receptors are located in the mucosal layer of the guinea pig ileum, and the impairment of the functions of these receptors by the intraluminal treatments leads to the blockade of the peristalsis.

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The effect of extracellular ATP on steroidogenesis in primary cultured bovine adrenocortical fasciculata cells was investigated. I observed that in the presence of extracellular Ca²⁺, ATP caused a dose-dependent elevation of intracellular Ca²⁺ ([Ca²⁺]_i) and induced steroidogenesis concentration- and time-dependently. However, in the absence of extracellular Ca²⁺, ATP had no effect on steroidogenesis. In the presence of extracellular Ca²⁺, calmodulin inhibitors inhibited the ATP-induced steroidogenesis, but dihydropyridine calcium channel blockers did not. Furthermore, ATP did not cause an elevation of cyclic AMP in bovine adrenocortical fasciculata cells even if extracellular Ca²⁺ existed. These results suggest that extracellular ATP might have an influence on bovine adrenocortical cells via the purinoceptor (P2Y) in connection with calcium mobilization, open the non-selective calcium channel and induce steroidogenesis by means of an elevation of [Ca²⁺]_i via the calcium-calmodulin system.

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The effects of tiropramide hydrochloride on Ca²⁺ induced contraction, cytoplasmic free Ca²⁺ levels and tissue cyclic AMP concentrations were investigated to elucidate the mechanisms of its antispasmodic action in the isolated detrusor from rats. Tiropramide inhibited the Ca²⁺ (3 mM)-induced contractions of the isolated urinary bladder depolarized in a Ca²⁺-free medium, and the IC₅₀ value was 3.3 × 10^-6 M. When tiropramide was added during the sustained phase of the K⁺ (60 mM)-contracture, IC₅₀ values of tiropramide for the contraction and the increased fluorescence were 1.9 × 10^-5 M and 16.4 × 10^-5 M, respectively. On the other hand, the IC₅₀ values for the K⁺-induced contraction and fluorescence after pretreatment of the isolated urinary bladder with tiropramide were 2.1 × 10^-5 M and 2.6 × 10^-5 M, respectively. Tissue cyclic AMP levels at 1 min after addition of 10^-5 M tiropramide were significantly increased. Papaverine, IBMX or forskolin potentiated the inhibitory effect of tiropramide on carbachol-induced contraction and its cyclic AMP-elevating effect. However, a good correlation between the degrees of potentiation of the inhibitory effect and the increase in cyclic AMP levels was not observed. The present results suggest that the smooth muscle relaxant activity of tiropramide in the isolated detrusor from rats may be intimately associated with predominant inhibition of Ca²⁺ influx and, to a lesser extent, an increase in intracellular cyclic AMP levels.

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The influence of acute exposures to standard (ST) and nicotine-reduced (NR) cigarette smokes on the plasma concentration of orally administered indomethacin (IM, 5 mg/kg) was investigated in rats. IM plasma concentrations in the ST- and NR-groups were lower than those in the non-smoking control group, while the lowered effect in the NR-group was slightly weaker than in the ST-group. These results suggest that the plasma concentrations of IM administered orally are lowered by the acute exposure of cigarette smoke, and this influence may be attributed largely to constituents other than nicotine in the cigarette smoke as well as slightly attributable to nicotine.

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ICR mice were grouped according to 1) housing environment: individual (I) or aggregated (A) and 2) timing of drug administration: midlight (L) or middark (D), i.e. I-L, I-D, A-L, A-D groups. Theophylline was orally administered at midlight or middark. The results showed that both social environment and timing of drug administration exerted significant influence on the pharmacokinetics of theophylline. These data may suggest the importance of considering many non-drug factors in toxicological studies with experimental animals.

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The effect of reserpine on vascular and intestinal smooth muscles was examined. In these muscles, reserpine inhibited the high K⁺-induced contraction, and this inhibitory effect was antagonized by the increase in external Ca²⁺ concentration and also by a Ca²⁺ channel activator, Bay k8644. In rabbit aorta, increases in cytosolic Ca²⁺ level and muscle tension due to high K⁺ were inhibited in parallel by reserpine. These results suggest that reserpine inhibits L-type Ca²⁺ channels to inhibit smooth muscle contraction.

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Vasodepressor mechanisms of adenosine were investigated in spinally-anesthetized dogs. An i.v.-infusion of adenosine (0.1-10 μmol/kg/min) caused a slowly developing and sustained decrease in blood pressure (BP). This vasodepression was antagonized by glibenclamide, a blocker of ATP-sensitive K⁺ (K_ATP) channels. On the other hand, a transient decrease in BP caused by a single bolus i.v.-injection of adenosine was not antagonized by glibenclamide in our previous study. These results suggested that the opening of K_ATP channels is gradually recruited in the vasodepressor mechanisms for adenosine-induced sustained vasodepression.

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Phenylephrine displacement curves for the specific binding of [³H]prazosin in the membrane fraction prepared from rabbit thoracic aorta showed high- and low-affinity sites with slope factors significantly less than unity. The irreversible α_1B-antagonist phenoxybenzamine shifted the binding sites to single high affinity sites with a slope factor close to unity in the presence of the metabolically stable GTP analog GTPγ-S. These results indicate that phenoxybenzamine may have affected selectively the low affinity site to phenylephrine in the presence of GTPγ-S.

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The effects of N^G-nitro-L-arginine methyl ester (L-NAME), the nitric oxide (NO) synthase inhibitor, on gastric HCO₃^- secretion were examined in anesthetized rats. Intravenous administration of L-NAME (1, 2.5, 5 mg/kg) increased HCO₃^- secretion in a dose-related manner. This effect of L-NAME was mimicked by N^G-mono-methyl-L-arginine (50 mg/kg, i.v.) and was antagonized significantly by concurrent administration of L-arginine but not D-arginine (200 mg/kg, i.v.). These results indicate that gastric HCO₃^- secretion is stimulated by inhibition of NO biosynthesis.

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The nucleus basalis magnocellularis (nbm)-lesioned rat is considered to be a model of the cholinergic dysfunction observed in the cerebral cortices of Alzheimer''s disease patients. The cholinergic markers, acetylcholine release and choline acetyltransferase activity, were decreased in the cerebral cortex of the nbm-lesioned rat. Kangenkaryu (KAN), a Chinese traditional medicine, is a typical prescription for the treatment of symptoms related to blood circulation deficiency. Orally administered KAN following the nbm lesion significantly preserved the cholinergic markers. The present results indicate that KAN may preserve the activity of cholinergic neurons in the cerebral cortex after the nbm lesion.

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We examined the effects of 1-methyl-4-phenylpyridinium ion (MPP⁺) on the release of DA in rat striatum by the in vivo microdialysis technique. For this study, we made a suitable microdialysis probe from a 22-G needle, microliter pipette tip, silica tube and polyethylene tube. Such a repairable microdialysis probe can be easily made from readily available and inexpensive materials. DA release, as determined by the 3-methoxytyramine level, was dose-dependently increased by MPP⁺ (1-10 mM). Only the presence of a 1 mM concentration of MPP⁺ in the dialysate significantly decreased the level of the DA metabolite DOPAC, while administration of higher MPP⁺ concentrations resulted in no significant change.

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