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KMID : 0368019900130010087
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Journal of Soonchunhyang University
1990 Volume.13 No. 1 p.87 ~ p.93
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Effects of Cyclouxine E on Drug-Induced Contractions and Potassium-Activated Calcium Channel in al Stomach Strip of the Rat
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Abstract
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For several years, we investigated the pharmacological actions of several substances isolated from Buxus microphylla var koreana Nakai, which had been used as folk remedies of malaria and venereal diseases. Buxuletin has a diuretic effects in rats. Cyclobuxine D(C_(25)H_(42)ON_(2)), a steroidal alkaloid, exerted an antiinflammatory action, hypotensive and bradycardic effects in rats, and negative isotropic action in several smooth muscles.
In the present study, I isolated an alkaloid from the acetone insoluble fraction of the strong bases of this plant. This alkaloid was identified as a steroidal alkaloid contained a cyclopropane ring by physical and chemical methods. It is a derivative of cyclobuxine D and named cyclobuxine E(C_(24)H_(38)ON_(2)). I examined the effects of cyclobuxine E on the contractile responses induced by acetylcholine and barium chloride and potassium-activated calium channel in a stomach strip of the rat. Acetylcholine produced contraction by inducing calcium influx through receptor operated calcium channels. Barium activates directly the contractile protein of smooth muscles. Cyclobuxine E inhibited significantly the acetylcholine and barium chloride-induced contractions. The isolated smooth muscle from the rat stomach was immersed calcium-depleted, potassium-depolarizing solution. After ten minutes, 1, gmM CaC12 was added to muscle bath and elicited a significant increase in muscle tension. This contractile response was not altered by atropine, but verapaml(calcium channel blocker) inhibited significantly the contractile response. Cyclobuxine E inhibited significantly the contractile response of the high potassium-depolarized rat stomach to calcium. In addition, cyclobuxine E introduced at a point which the contractile response
had reached its maximal level, caused the muscle to exhibit a rapid loss of tension. Based on these experimental results, I proposed the possibility that the inhibitory action of cyclobuxine E on the isolated rat stomach strip may due to inhibiting the transmembrane influx of calcium ion through potassium-activated calcium channel (probably, voltage-dependent calcium channel).
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