Radioimmunoassayable plasma motilin in man. Secretagogues, insulin-induced suppression, renal removal, and plasma components.

In normal humans, significant motilin increases were found after meal ingestion, intraduodenal infusion of fat, and intraduodenal infusion of physiological HCl doses. Only a non-significant plasma motilin increase was found in response to intraduodenal infusion of cattle bile. Plasma motilin decreased significantly after an intravenous insulin injection. During routine cardiac catheterization in a group of 10 patients plasma motilin was significantly lower in the renal vein than in the femoral vein, femoral artery, right atrium, and hepatic vein, suggesting that the kidneys participate in the removal of motilin from the circulation. Fasting and oral fat-stimulated plasma motilin immunoreactivity eluted in two peaks on a Sephadex G-50 Fine column. The two peaks behaved identically with porcine motilin in dilution series.