Effects of morphine on net water absorption, mucosal adenylate cyclase activity and PGE2 metabolism in rat intestine.

Morphine (10 mg/kg s.c.) was shown to increase net basal water and electrolyte absorption in rat ileum and colon perfused in vivo. These effects were significantly greater in the ileum. Under the same conditions of dosage and time course of administration the activities of relevant mucosal enzymes were studied. Ileal mucosal adenylate cyclase stimulated by prostaglandin E2 (PGE2) in vitro was inhibited by morphine pretreatment. Colonic stimulated cyclase activity was unaffected as were basal activities in both regions. Morphine did not alter the activities of enzymes involved in PGE2 metabolism and is unlikely to act by modulating endogenous PG levels. Transport ATPase activities, were also unchanged in morphine treated animals. These results are discussed in relation to the mechanism of action of morphine on intestinal mucosa.