Effects of cholecystokinin, food intake and cephalic stimuli on plasma levels of amylase, lipase, and immunoreactive cationic trypsinogen in rats.

Plasma levels of amylase, lipase, and immunoreactive cationic trypsinogen (ICT) were monitored in conscious rats to study the effects of cholecystokinin octapeptide (CCK-8) plus secretin administration, cephalic stimuli, and food intake. Stepwise increasing doses of CCK-8 (1, 5, 15, 30 Ivy dog units: IDU/kg/h) caused significant dose-related increases in plasma levels of each enzyme in a similar manner as those previously observed for response patterns of CCK-induced exocrine protein secretion in the same species. ICT showed the greatest response to CCK-8 with a maximal concentration 30 times above basal levels resulting in the steepest slope of the dose-response curve. Plasma lipase showed a maximal response that was 5 times above the basal level, while the plasma amylase level was increased only by 50% at the maximal response. Computed ED50 of CCK-8 for each enzyme confirmed this relative sensitivity of the response: 3.0, 8.7, 11.0 IDU/kg/h for ICT, lipase, and amylase, respectively. Plasma levels of amylase and lipase did not change significantly in response to the intake of either a liquid diet or fiber pellets containing no caloric value. Plasma ICT levels, however, were elevated significantly by 23 and 53% at the time when the liquid diet or fiber pellets were given and when cephalic stimulation appeared maximally induced. The increased levels declined thereafter and were no longer significantly different from the basal levels for postprandial 2 h.(ABSTRACT TRUNCATED AT 250 WORDS)