The effects of prostaglandins F2 alpha and E2 on the motility of the cat colon in vitro.

Controversy exists with respect to the motor effects of prostaglandins (PG) in the colon. We studied the actions of the prostaglandins F2 alpha and E2 on the spontaneous and stimulated contractions of the circular muscle of the cat colon in vitro. Both prostaglandins enhanced contractile activity. PG F2 alpha was more effective than PG E2, the ED50 were 4.2 X 10(-9) M and 2 X 10(-7) M, respectively. The prostaglandin antagonist 8 ethoxycarbonyl-5-methyl-10,11-dihydroxy-PG A1-ethyl-ester (HR 546) in a concentration of 10(-7) M shifted the ED50 of PG F2 alpha to the right by 1 log unit and unmasked motor stimulatory actions of low PG F2 alpha concentrations (10(-11) and 10(-10) M). The latter effect was atropine sensitive. In conclusion, PG F2 alpha and PG E2 stimulate contractions of the circular colon muscle at concentrations naturally occurring in the gut. It is conceivable that they play a role in the control of colonic motility, particularly in diseases like ulcerative colitis and Crohn's disease.