Vasoactive intestinal polypeptide appears to be one of the mediators in misoprostol-enhanced small intestinal transit in rats

Background and Aims: Prostaglandin analogs have the pharmacologic effect of speeding up small intestinal transit (SIT). It remains unknown whether som e gut peptides also mediate this enhancement. We studied the effect of miso prostol on rat SIT and looked at the role of vasoactive intestinal polypept ide (VIP) release during its action. Methods: A group of rats initially received oral misoprostol treatment of 1 , 10, 50 and 100 mug/kg, respectively. By using orally fed charcoal as a mo tility marker, the SIT was assessed at 30 min following oral misoprostol tr eatment. Another group of rats received misoprostol as an intraperitoneal i njection in similar doses to the group above. The small intestinal transit was computed for this group at 30 min following misoprostol injection via a n instilled radiochromium motility marker that went through a previously pl aced intraduodenal catheter. The plasma VIP level was measured by using a r adioimmunoassay kit. Results: Neither charcoal evaluated transit nor the plasma VIP level was in fluenced by the lower doses of oral misoprostol treatment (1 and 10 mug/kg) , whereas other doses enhanced SIT and diminished the plasma VIP level (P < 0.01). The similar effects on radiochromium computed SIT (P < 0.01) and pl asma VIP levels were obtained in tubed rats following misoprostol intraperi toneal treatment. The SIT results correlated negatively with plasma VIP lev els. Conclusions: Enhanced SIT and diminished VIP levels are found in rats follo wing misoprostol treatment. It appears that inhibited VIP release is one of the mechanisms in misoprostol-enhanced SIT. (C) 2000 Blackwell Science Asi a Pty Ltd.