Effects of cholecystokinin and hydrocortisone on DNA and protein synthesis in immature rat pancreas

Pancreatic function in CCK-deficient mice: adaptation to dietary protein does not require CCK

A CCK-deficient mouse mutant generated by gene targeting in embryonic stem cells was analyzed to determine the importance of CCK for growth and function of the exocrine pancreas and for pancreatic adaptation to dietary changes. RIAs confirmed the absence of CCK in mutant mice and demonstrated that tissue concentrations of the related peptide gastrin were normal. CCK-deficient mice are viable and fertile and exhibit normal body weight. Pancreas weight and cellular morphology appeared normal, although pancreatic amylase content was elevated in CCK-deficient mice. We found that a high-protein diet increased pancreatic weight, protein, DNA, and chymotrypsinogen content similarly in CCK-deficient and wild-type mice. This result demonstrates that CCK is not required for protein-induced pancreatic hypertrophy and increased proteolytic enzyme content. This is a novel finding, since CCK has been considered the primary mediator of dietary protein-induced changes in the pancreas. Altered somatostatin concentrations in brain and duodenum of CCK-deficient mice suggest that other regulatory pathways are modified to compensate for the CCK deficiency.

The anticoordinate changes of pancreatic lipase and colipase activity to amylase activity induced by adrenalectomy in normal and diabetic rats

The effect of adrenalectomy (Adx) on pancreatic lipase and colipase activities in normal, streptozotocin-induced diabetic, and obese Zucker rats was studied. It was found that Adx induced a rapid decrease in amylase activity, a rapid increase in lipase activity, and a slow increase in colipase activity in normal rats. Twenty days after Adx, the levels of amylase activity were 70% lower than control, whereas the activities of lipase and colipase were 55 and 25% higher than control, respectively. The replacement of hydrocortisone normalized the changes in the three enzyme activities. Injection of insulin partially corrected the amylase activity, but had no significant effect on the activities of lipase and colipase. In streptozotocin-induced diabetic rats and obese Zucker rats, amylase activity was decreased, and lipase and colipase activities increased, compared to normal rats. These changes of enzyme activity were further enhanced by Adx. It is concluded that Adx results in an anticoordinate change in pancreatic lipase, colipase, and amylase activities, suggesting that glucocorticoid also influences the synthesis of the pancreatic lipolytic enzymes.

Endogenous cholecystokinin reduces feeding in young rats

The hypothesis that endogenous cholecystokinin (CCK) released from the small intestine during feeding causes satiety was tested in rat pups, 9 to 12 days old. Intragastric administration of soybean trypsin inhibitor, a procedure that releases CCK from the small intestine, decreased the subsequent intake of a test meal. This effect was reversed by prior treatment with MK-329, a selective antagonist of CCK at alimentary-type CCK (CCK-A) receptors. Thus, endogenous, small intestinal CCK can cause satiety in the neonatal rat and this effect involves CCK-A receptors.