EFFECTS OF ETHANOL ON CONTRACTILE RESPONSE OF GALL-BLADDER ISOLATED FROM GUINEA-PIG

The effects of ethanol treatment in vitro and in vivo on gall bladder contraction were investigated using gall bladder strips isolated from guinea pigs. In vitro pretreatment of the strips with ethanol at a con centration of over 50 mM significantly attenuated the reactivity and s ensitivity of contractile responses to KCl, acetylcholine and histamin e in a concentration-dependent manner. Indomethacin treatment or remov al of extracellular calcium remarkably reduced gall bladder contractil e response to acetylcholine. The depressive effect of ethanol in vitro on gall bladder contraction was also noted in the presence of indomet hacin or absence of calcium in the medium. The concentration-response curve of calcium-induced contraction in 40 mM KCl-depolarized gall bla dder strip shifted to the right on pretreatment with ethanol. In the c ase of strips following the chronic administration of 3% ethanol solut ion ad libitum for 4 weeks, contractile responses to KCl, acetylcholin e and histamine did not differ, compared to those in the pair-fed grou p. This chronic ethanol administration induced tolerance to the acute inhibitory effect of ethanol on gall bladder contractile responses to the agonists. Ethanol is thus shown to exert direct inhibitory action on gall bladder contraction by lowering the calcium sensitivity of the contractile apparatus of smooth muscle; it is unlikely that ethanol c onsumption would affect gall bladder motility in vivo, owing to the to lerance produced toward the acute inhibitory action of ethanol.