Evidence for Modulation of Motilin Secretion by Pancreatico-Biliary Juice in Health and in Chronic Pancreatitis*

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Abstract
The gut hormone motilin can initiate the inter-digestive migrating motor complex. There are synchronous cyclic changes in plasma motilin-like immunoreactivity (MLI) levels and pancreatico-biliary secretion during the interdigestive period which may be causally related. The purpose of this study was to investigate the role of pancreatico-biliary secretion into the gut as a modulator of plasma MLI concentrations. In six healthy subjects, the mean basal plasma MLI level was 130 ± 16pg/ml. Infusion of cholecystokinin octapeptide (CCK-8) stimulated MLI secretion, with an integrated (30 min) response of 2028 ± 340 pg/min·ml. Intraduodenal perfusion of pancreatico-biliary juice produced a similar increase in plasma MLI, with a 30 min integrated response of 2190 ± 270 pg/min ml. Neither enzyme activity, osmolarity, or pH accounted for the response. n I six patients with exocrine pancreatic insufficiency, although their mean basal plasma MLI concentration of 205 ± 44 pg/ml was significantly higher than that observed in healthy subjects, there was no significant plasma MLI increase after CCK-8 infusion. Pancreatic exocrine secretion was severely compromised in these patients, as evidenced by the markedly reduced peak lipase (3.8 ± 0.6 kU/h) and trypsin (2.4 ± 0.5 kU/h) outputs. In contrast, infusion of pancreatico-biliary juice obtained from healthy subjects caused a rise in plasma MLI, with a 60 min integrated response of 3912 ± 1031 pg/min·ml, which was similar to that of 3947 ± 472 pg/min·ml in healthy subjects. We conclude that there is an undefined factor in pancreatico-biliary juice that stimulates MLI release. A deficiency of pancreatic exocrine secretion may be responsible for the impaired MLI response to CCK-8 stimulation in chronic pancreatitis. Since MLI is known to initiate the formation of the interdiges-tive migrating motor complexes, diminished motilin release secondary to pancreatic exocrine deficiency may result in disordered gastrointestinal motor activity in patients with chronic pancrea-titis.