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 some gut peptides also mediate this enhancement. We studied the effect of misoprostol on rat SIT and looked at the role of vasoactive intestinal polypeptide (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 motility marker, the SIT was assessed at 30 min following oral misoprostol treatment. Another group of rats received misoprostol as an intraperitoneal injection in similar doses to the group above. The small intestinal transit was computed for this group at 30 min following misoprostol injection via an instilled radiochromium motility marker that went through a previously placed intraduodenal catheter. The plasma VIP level was measured by using a radioimmunoassay kit. Results: Neither charcoal evaluated transit nor the plasma VIP level was influenced 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 plasma VIP levels were obtained in tubed rats following misoprostol intraperitoneal treatment. The SIT results correlated negatively with plasma VIP levels. Conclusions: Enhanced SIT and diminished VIP levels are found in rats following misoprostol treatment. It appears that inhibited VIP release is one of the mechanisms in misoprostol-enhanced SIT. (C) 2000 Blackwell Science Asia Pty Ltd.