^<45>Ca-loaded single smooth muscle cells were prepared from taenia coli of guinea pig. The cells were perfused continuously with physiological salt solution on membrane filter with pore size of 12 μm and radioactivity in the effluent was determined. The ⁴⁵Ca-efflux curves consisted of two straight lines in semilogarithmic figure representing loosely and tightly bound calcium compartments with half time of 1.87±0.27 and 6.78±0.43min, respectively. The loosely bound calcium was supposed to be localized on plasma membrane. Size of the tightly bound ⁴⁵Ca was dependent on period for calcium-depletion of the preparation prior to ⁴⁵Ca-loading. The efflux was stimulated by acetylcholine and the stimulated efflux returned to the spontaneous efflux level instantly after removal of acetylcholine. This stimulation was abolished by atropine. Repetitive stimulation failed to increase ⁴⁵Ca-efflux while the rate of the spontaneous ⁴⁵Ca-efflux did not change significantly. These results suggested that, in taenia coli of guinea pig, at least three calcium compartments existed, loosely bound calcium, tightly bound calcium and more tightly bound calcium which can be released by acetylcholine, in addition to calcium in extracellular fluid. Advantages and disadvantages of using single smooth muscle cells for investigation of calcium movement and some technical improvement for determination of ⁴⁵Ca-efflux from single cells were described.

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In view of the strong inhibitory effects of the carboxamide-methylated Lchain (Fr.I-L) from human IgGon gastric ulceration and juice secretion, we carried out various experiments to clarify the mechanism of its action and obtained the following results. Fr. I-L inhibited the gastric ulceration induced by phenylbutazone or aspirin in rats, but no appreciable effect was observed on stress or acetic acid ulceration. The distribution of ¹⁴Clabelled Fr. I-L increased particularly in the stomach mucous membrane of rats after the intravenous or intraperitoneal administraion. The hexosamine content in the gastric mucous membrane, reduced by the treatment with phenylbutazone, aspirin or pylorus-ligation, was recovered by the administration of Fr.I-L to an intact level. The high total of hexosamine levels found in the gastric juice after aspirin treatment or pylorus-ligation were decreased by the injection of Fr.I-L or cimetidine. The histochmical observation revealed that the concomitant administration of Fr. I-L with phenylbutazone or aspirin prevented the abolishment of Hematoxylin-Eosin, Periodic Acid Schiff and Alcian Blue staining polysaccharides from the stomach epithelial cells.

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Protective effects of glutathione peroxidase, glutathione S-transferase purified from human liver and superoxide dismutase against lipid peroxidation were investigated. In the presence of glutathione, lipid hydroperoxides found in microsomal membrane were decomposed by glutathione peroxidase and cationic glutathione S-transferase, but anionic glutathione S-transferase had no effect on them. Superoxide dismutase exhibited antioxidation effect by preventing accumulation of lipid hydroperoxides. Serum lipid hydroperoxides existing in low density lipoprotein fraction were also decomposed by glutathione peroxidase and cationic glutathione S-transferase. These findings suggest that the hydroperoxide level, which has high toxicity, could be controlled by these glutathione-dependent glutathione peroxidase and cationic glutathione S-transferase.

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The role of sodium ion on the relaxant action of papaverine in guinea-pig taenia coli contracted by hypertonic 40 mM KCl were studied by manipulating the external soidum ion concentration and compared with those of its allied antispasmodics, Aspaminol and benactyzine. Whereas all of the three antispasmodics relaxed the taenia in all media used herein, their relaxant activities were declined by eliminating sodium ion from the bathing media. The declined relaxant activities were restored by re-introducing sodium ion to the solution depending on the amount of sodium ion but sodium ion dependencies of the restoration were not equal for each. In a solution containing 20 mM sodium ion, almost complete restoration was encountered with papaverine, while displayed only a slight restoration with Aspaminol and benactyzine. When a small amount of sodium ion was applied to the taenia before or after the treatment with the antispasmodics, the relaxation in response to papaverine was augmented, but those in response to Aspaminol and benactyzine were not affected. All of the three antispasmodics inhibited the cellular ⁴⁵Ca-uptake in all media. While their inhibitory activities were reduced by eliminating sodium ion from the media and were not restored so markedly by re-introducing 20 mM sodium ion to the solution. From these findings, it is suggested that papaverine may induce the smooth muscle relaxation not only by inhibiting the Ca-influx independently of the presence of sodium ion but also by other mechanisms sensitive to sodium ion, by contrast, Aspaminol and benactyzine may evoke the relaxation through mechanisms less sensitive to the presence of sodium ion, which include the inhibition of Ca-influx. Since the ability of papaverine to increase the cellular cyclic AMP content remained unchanged even in the Na-free solution, parts of cyclic AMP on the sodium ion sensitive mechanisms were also duscussed.

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The roles of the renin-angiotensin system (RAS) and aldosterone in the pathogenesis of nephrotic syndrome were investigated with rats following subcutaneous injections of puromycin aminonucleoside (PAN) for 7 d. Prominent reduction in plasma renin activity (PRA) was observed at day-15 after the initial treatment with PAN preceded by the onset of the nephrosis and there was no significant difference in plasma aldosterone concentration (PAC) between the nephrosis and normal control groups despite the higher levels obtained in the nephrosis animals. Although we could not elucidate the precise mechanism of reduction in PRA, it was suggested that neither the RAS nor aldosterone secretion played a primary role in the pathogenesis of the nephrosis. PAN-induced nephrosis is interesting in studying the pathophysiological mechanism of the lowered activity of plasma renin in some patients with nephrotic syndrome.

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The purpose of this investigation is to correlate between trimethadione (TMO) metabolism and hepatic microsomal drug-oxidizing activities in different animal species (mouse, hamster, rat and rabbit). A good correlation was obtained between the plasma concentration ratio of 5, 5-dimethyl-2, 4-oxazolidinedione (DMO) to TMO and relative activities of aminopyrine (γ=0.999 at 1 h, p<0.01;γ=0.994 at 2 h, p<0.01) and TMO (γ=0.988 at 1 h, p<0.02;γ=0.975 at 2 h, p<0.05) N-demethylase, and aniline (γ=0.993 at 1 h, p<0.01;γ=0.979 at 2 h, p<0.01) hydroxylase. These results indicate that the values of plasma DMO/TMO ratio determined at an appropriate time period following its administration would be reflecting the degree of hepatic drug-oxidizing capacity in various experimental animal species. These findings thus suggest that in vivo TMO metabolism would be a useful drug for predicting hepatic drug-oxidizing capacity in humans.

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The effcts of sodium nitroprusside (NaNP) and diltiazem on CaCl₂-, KCl- and histamine-induced contractile responses were studied in isolated rabbit basilar artery, aorta, taenia coli and trachea. NaNP reduced CaCl₂-induced maximal contractions in basilar artery and aorta, but little affected those in taenia coli and trachea. NaNP reduced histamine-induced maximal contraction markedly in aorta but slightly in basilar artery and taenia coli. The reduction in aorta was reversed by increasing CaCl₂ concentration in bathing medium. NaNP inhibited histamine-induced contractions of basilar artery, aorta and taeniacoli in Ca-free medium. Diltiazem reduced CaCl₂-induced maximal contractions in basilar coli in Ca-free medium. Diltiazem reduced CaCl₂-induced maximal contractions in basilar artery and aorta, whilst it caused a parallel shift of concentration-response curves for CaCl₂ to the right in taenia coli and trachea. Diltiazem reduced histamine-induced maximal contractions in basilar artery and taenia coli. These reductions were reversed by increasing CaCl₂ concentration in bathing medium. Diltiazem strongly inhibited histamine-induced contraction of taenia coli in Ca-free medium. The effects of NaNP and diltiazem on KCl-induced contractions both in normal (Ca;2.5 mM) and in high Ca (Ca;12.5 mM) media were also studied. From the results obtained in this study, the actions of NaNP and diltiazem were considered to vary with the type of smooth muscle or the condition eliciting contraction. Their possible mechanisms were discussed in this paper.

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The genetic effect of arsenite (AsO^-₂) and arsenate (HAsO²₄-) on the cells of E.coli B (argF^-) tester strains was investigated. Both the arsenics, which did not show mutagenic effect on the tester strains, reduced UV-induced mutation frequency of H/r30R (wild-type ; Exc⁺ Rec⁺) cells, while they did not change that of Hs30R (uvrA^-; Exc^-Rec⁺) cells. To elucidate the mechanism of this antimutagenicity, modifying effect of the arsenics on UV-induced cytotoxicity for Hs30R and NG30 (recA^-; Exc⁺Rec^-) cells was examined. In a nutrient medium containing the arsenics, the survived cell fraction of NG30 after ultraviolet (UV) irradiation was markedly increased, whereas that of Hs30R was not altered. When the UV-exposed NG30 cells were subjected to recovery incubation in a nutrient medium containing the arsenics, the survived cell fraction was remarkably increased before the cell proliferation in a similar manner as liquid-holding recovery observed in an arsenic-free and non-nutrient medium in which DNA replication was suppressed. The arsenics were found to cause a delay of DNA replication in UV-irradiated NG30 cells. These results indicate that arsenite and arsenate enhance the error-free excision repair of UV-damaged DNA by retarding the DNA replication and thus by prolonging the period for excision repair. This may lead to the reduction in UV-induced mutation.

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Young chickens with inefficient blood-brain barrier were employed to study the effects of aliphatic ω-aminosulfonic acids with varying numbers of carbon chains on the central nervous system. Each of the amino acids was intraperitoneally administered to unrestrained and unanesthetized animals, to investigate its effects upon their behavior and electroencephalogram (EEG). ω-Amino acid with a short-chain structure (3-aminopropanesulfonic acid) had a depressing effect similar to that of γ-aminobutyric acid which is known as a depressant amino acid. On the other hand, the ω-amino acids with long-chain structure (5-aminopentanesulfonic acid and 6-guanidinohexanesulfonic acid) acted as excitants, induced convulsions and developed typical biphasic spikes with high amplitudes in the EEG. The spikes appeared early, and could be detected at the excitant stage before convulsion. In contrast, with the administration of convulsant drugs, the spikes appeared only after the occurrence of convulsion. However, a high dose (1-9g/kg) of the ω-amino acids was needed to develop their effects. These results suggest that young chickens are valuable in clarifying the characteristic behavior and the brain electrical activity of ω-amino acids. But the ω-amino acids cannot easily pass through the blood-brain barrier in young chicken.

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The vaginal absorption of a potent luteinizing hormone-releasing hormone analog (leuprolide), and the gonadotropins (luteinizing hormone and follicule-stimulating hormone)-releasing response after continuous vaginal and subcutaneous administration of the analog to rats were determined by the redioimmunoassay. A marked suppressive effect on the gonadotropin-releasing response along with long-lasting serum levels of leuprolide were paradoxically observed after consecutive 3-d vaginal administration of the analog at doses of 1 μg/kg or greater. Pituitary function recovered progressively with cessation of the treatment but was not complete 4 d after cessation. Continuous vaginal and subcutaneous infusion resulted in an almost complete inhibition of both gonadotropins response. It is suggested that effective desensitization of the pituitary gonadotropin response is elicited by continuous administration of leuprolide and, therefore, the vaginal administration resulting in prolonged serum levels of the analog could be preferable as a self-administration method for medical treatments such as anti-tumor therapy and birth control.

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