The prostaglandin E2-induced contraction in the ileal longitudinal smooth muscle isolated from various animal species.

Abstract

PGE2 was examined for the effect on contractile response of the ileal longitudinal muscle isolated from eight animal species, monkey, dog, cat, rabbit, guinea pig, vole, rat and mouse. In isotonic recording, PGE2 induced a sustained contraction in the ileum isolated from monkey and cat. It caused a transient contraction followed by a relaxation in the ileum isolated from other animal species. The sensitivity of ileal strips to the contractile effect of PGE2, as estimated from 50% effective dose (ED50) of PGE2, was in the order of guinea pig>vole>rabbit>rat>mouse>monkey>dog>cat. On the other hand, ED50 values of acetylcholine (ACh) were in the concentrations ranging from 1×10-7 M to 5×10-7 M except for guinea pig. Thus, there were species differences in the sensitivity of the ileal strips to PGE2 but not to ACh. Further, the contractile responses to PGE2 in the intestine from these animal species were divided into three groups using various inhibitors. In the group 1 animals consisting of herbivorous like rabbit, guinea pig and vole, PGE2 contractions were inhibited by TTX, atropine, scopolamine or SC-19220. In the group 2 animals consisting of carnivorous like dog and cat, PGE2 contractions were inhibited by scopolamine and SC-19220 but not by atropine or TTX. In the group 3 animals consisting of omnivorous like monkey, rat and mouse, PGE2 contractions were inhibited only by SC-19220.