Contribution of prostaglandin to the contraction induced by catecholamines in the isolated gallbladder of the guinea-pig.

Possible contribution of prostaglandins to the mechanical response produced by catecholamines was investigated in the isolated strips of the guinea-pig gallbladder. The contraction by catecholamine was blocked by an alpha-blocker, phentolamine (10(-6)M and relaxation was blocked by a beta-blocker, propranolol (10(-6)M. The rhythmic spontaneous motility and intrinsic tone were markedly inhibited by a prostaglandin synthesis inhibitor, indomethacin (10(-7)M. Furthermore, exogenous prostaglandins F2 alpha, E1 and E2 produced potent stimulant actions on gallbladder and the order of potency was found to be E2 > E1 > F2 alpha. The contractile response of catecholamines was abolished almost completely by indomethacin (10(-7)M. Even after the muscle tone was elevated by exogenous prostaglandin after treatment with indomethacin, catecholamine produced no contractile response, although it still relaxed the preparation through activation of beta-receptor. Based on these results, it was suggested that endogenous prostaglandins appear to be contributed to the alpha-action of catecholamines in the isolated guinea-pig gallbladder.