Misoprostol-inhibited rat gastric emptying is independent of gastric inhibitory polypeptide release

We studied the effects of orally or intraperitoneally administrated misoprostol on rat gastric emptying and looked what was the role of gastric inhibitory polypeptide (GIP) in this emptying. The rats initially received oral misoprostol at doses of 1, 10, 50, and 100 microg/kg. Another group of rats received misoprostol intraperitonally at doses of 10, 50, 250, and 500 microg/kg. Using an oral radiochromium motility marker, the liquid gastric emptying was measurement 30 min after misoprostol treatment. The plasma GIP levels were measured by a home-made radioimmunoassay kit. Oral treatments at the doses of 1 and 10 microg/kg did not influence emptying, whereas other doses delayed emptying (p < 0.01). Except the 10- microg/kg injection, other doses exhibited a dose-dependent inhibition in emptying (p < 0.01). Neither oral feeding nor intraperitoneal injection changed plasma GIP levels. We conclude that liquid gastric emptying is disturbed after various routes of misoprostol treatment; GIP appears less important in the misoprostol-mediated gastric emptying.