Plasma motilin levels in duodenal ulcer and effect of a truncal vagotomy and hypoglycaemia

Motilin and clinical application

Motilin is a regulatory polypeptide of 22 amino acid residues and orginates in motilin cells scattered in the duodenal epithelium of most mammals and chickens. Motilin is released into the general circulation at about 100-min intervals during the interdigestive state and is the most important factor in controlling the interdigestive migrating contractions. Recent studies have revealed that motilin stimulates endogenous release of the endocrine pancreas. Clinical application of motilin as a prokinetic has become possible since erythromycin and its derivatives were proved to be nonpeptide motilin agonists.

Effect of vagal blockade on food- and hormone-stimulated release of pancreatic polypeptide and motilin in dogs

Vagal control of food- and hormone-stimulated release of pancreatic polypeptide (PP) and motilin was investigated in four conscious dogs by examining the effect of cryogenic vagosympathetic blockade. The postprandial PP response of 189 +/- 7 pM was totally, although reversibly, inhibited to 58 +/- 11 pM with the vagi blocked. Similarly, bombesin-, CCK-OP-, or neurotensin-stimulated PP release was abolished. Although the PP response to intraduodenal perfusion of an elemental diet was also reduced by blockade, the 52 +/- 15% inhibition was less than observed with the meal. In contrast to PP, plasma motilin fell after the meal from a fasting level of 128 +/- 16 pM to a nadir of 52 +/- 7 pM. Vagal blockade reversed this decline as plasma motilin rose to a peak of 121 +/- 18 pM with a pattern resembling the motilin response in the interdigestive state. This motilin increment during blockade was inhibited by atropine and by infusion of porcine PP. Plasma motilin also fell with the elemental diet, but this response was not affected by blockade. During infusion of bombesin, plasma motilin rose by 60 +/- 9 pM; vagal blockade augmented this increment twofold. Thus, the PP response to a meal and to hormonal stimulation is controlled by a vagal cholinergic excitatory pathway. However, intestinal release of PP is mediated in part by the vagus and in part by a vagally independent mechanism which may be neural or hormonal. Alternatively, vagal noncholinergic inhibition is a major mechanism modulating the motilin response after oral food but motilin release exclusively from intestinal nutriments is mediated by nonvagal, noncholinergic mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of naloxone on circulating metabolites, glycoregulatory hormones and gut peptides during pelvic surgery

The role of endogenous opioid peptides in mediating the endocrine and metabolic response to pelvic surgery was investigated. Fourteen patients were studied; seven were infused with the specific opioid antagonist, naloxone, at a rate of 20 micrograms kg-1 (body weight) hr-1, while the remainder acted as a control group. Naloxone exacerbated the glycaemic response to surgery but had no statistically significant effect on changes in the glycoregulatory hormones, pancreatic glucagon, insulin, cortisol and growth hormone. However, there was a wide individual variation in the glucagon response to naloxone with marked stimulation in some patients. Naloxone infusion increased plasma pancreatic polypeptide secretion during the 1st hour of surgery and reversed the decline in plasma motilin concentrations, but had no effect on circulating somatostatin, vasoactive intestinal polypeptide, gastrin, enteroglucagon and neurotensin values. We conclude that endogenous opioid peptides have only a limited role in modulating the endocrine and metabolic response to surgery.