Prostaglandins and the contractile action of bradykinin on the longitudinal muscle of rat isolated ileum.

1. The effect of the prostaglandin synthesis inhibitors aspirin and indomethacin (Ind) was investigated upon contractions of the perfused isolated terminal ileum of the rat to bradykinin (Bk) or potassium chloride (KCl). The release of a prostaglandin-like substance (PGLS) from the ileum was simultaneously assayed on the rat fundus strip (RFS). 2. Aspirin (610 micro M) or Ind (28 micro M) reduced contractions of the ileum to Bk perfused over the mucosal surface but not to Bk perfused over the serosal surface. 3. After perfusion of either ileal surface the effluent potentiated the contractions of the RFS to Bk. No potentiation was observed in the presence of either Ind or aspirin. 4. Contractions of the RFS to Bk were potentiated by prostaglandin E2 (PGE2) (0.7 X 10(-12) M and 1.4 X 10(-12) M) but not by either a higher (2.8 x 10(-12) M) or a lower (0.35 X 10(-12) M) concentration of PGE2. No potentiation was observed with prostaglandin F2 alpha (PGF2 alpha) at the concentrations studied. 5. Only the contractile action of Bk acting on the mucosal surface of the rat isolated perfused ileum seems to involve prostaglandin synthesis.