<原著>諸種平滑筋のK-脱分極標本に対する低温効果とバナジン酸の影響
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概要
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Effects of cooling on high-K-depolarized smooth muscles of taenia coli, portal vein, ureter and vas deferens of guinea-pigs, and its modification by vanadate were studied, High-K-induced contractures of these smooth muscles were composed of the phasic and the tonic component of contraction. The tonic contractions of taenia coli and portal vein were greater than those of ureter and vas deferens ; all of them were sustained longer than 120 minutes. Cooling treatment applied during the tonic contraction caused relaxation in the taenia coli and portal vein, and contraction in the ureter and vas deferens. The tension development in the latter preparations was greatest at the temperature of 15℃, and was dependent on extracellular Ca. Vanadate of 2 mM induced tension development and potentiated greately the cooling-induced tension development of K-depolarized ureter and vas deferens. The effect could be observed only in the K-depolarized preparations and in the presence of Ca. In the taenia coli, cooling-induced relaxation was reversed into contraction in the presence of vanadate, whereas the effect was not observed in the portal vein. Ouabain of the concentration up to 1 mM could not potentiate the tension development of the ureter and vas deferens by cooling and also could not reverse the cooling-induced relaxation in the taenia coli. The relaxation by cooling observed in the portal vein may be explained by the decrease in Ca influx and/or in the contractile reaction of actin-myosin system. The cooling-induced tension development, observed in the ureter and vas deferens, on the other hand, may be brought about by the decrease in the Ca sequestering activity of plasma membrane and/or of sarcoplasmic reticulurn. Vanadate potentiates the cooling-induced tension development and reverses the cooling-induced relaxation presumably by promoting the inhibition of Ca sequestration by cooling. The inhibition of Na, K-ATPase may not be involved in the action of vanadate. The sensitivity of the Ca sequestering properties of membranous system to temperature and vanadate might vary among various smooth muscles.
- 近畿大学の論文
- 1987-12-25