[Effects of various natural prostaglandins on human gastrointestinal motility in vitro]

The effects of three natural prostaglandins, E1, E2 and F2alpha, on the human gastrointestinal tract were investigated by means of an in vitro technique. Prostaglandin F2alpha showed a stimulatory effect on all the segments examined and its activity was comparable to that of acetylcholine (threshold doses 0.5-2 mug). Prostaglandin E1 relaxed the circular muscles of the stomach (minimum active dose was 1 mug/ml) but contracted the longitudinal ones and taenia coli. Prostaglandin E2 showed an interesting inhibition of the stimulant effect of acetylchooline on circular muscles of the stomach (1 mug/ml) and a weak spasmogenic activity on the other tracts. The mechanism of action of prostaglandins has not been completely elucidated; it seems plausible to suggest a direct effect of the drugs on the smooth muscle, however the release of an unknown mediator cannot be excluded.