EFFECTS OF PROSTAGLANDINS E(1), E(2) AND F2-ALPHA ON CONTRACTILITY AND CAMP AND CGMP CONTENTS IN LOWER URINARY-TRACT SMOOTH-MUSCLE

Prostaglandin (PG) E(1), E(2) and F-2 alpha contracted smooth muscle strips from male adult rabbit urinary bladder. Contractile responses to each PG were significantly greater in urinary bladder body than in urinary bladder base. The magnitude of contractile response to each PG was F-2 alpha > E(2) > E(1) in both of the bladder body and the bladder base. These contractions were almost completely eliminated by a calcium entry blocker, verapamil but not by atropine, phentolamine, propranolol or tetrodotoxin. PG E(1) and E(2) significantly relaxed the male rabbit urethral smooth muscle strips, whereas PG F-2 alpha contracted the urethral smooth muscle strips. Cyclic adenosine monophosphate (cAMP) but not cyclic guanosine monophosphate (cGMP) increased significantly after administration of PG E(1) or E(2) in the urethral muscle strip. These results suggest that the regional differences in the magnitude of contractile responses to PG E(1), E(2) and F-2 alpha between the bladder dome and the base and also suggest the contractile differences of PG E(1) and E(2) for the urinary bladder and the urethra; contractions for bladder and relaxations for urethra. These results also demonstrate that contractions induced by PG E(1), E(2) and F-2 alpha in urinary bladder smooth muscles and by PG F-2 alpha in urethral smooth muscles are mainly mediated by calcium influx and that relaxations induced by PG E(1) and E(2) in urethral smooth muscles are mediated by cAMP but not by cGMP.