Delayed weaning and denial of solid food nibbling upon pancreatic acinar cell responsiveness to urecholine in neonatal rats.

Pancreatic response to urecholine was studied in rats which were fed maternal milk only until they reached 27 days of age. A group of pups which remained all the time with their mother were weaned at 21 days; over that nursing period, their pancreatic amylase concentration increased gradually, lipase started to decrease from day 23 while chymotrypsin remained constant. In those who were denied solid food from day 12, the amylase concentration fell significantly from day 23 to 27 while lipase and chymotrypsin rose rapidly. Delayed weaning was associated with significant decreases in basal and urecholine-stimulated amylase secretion from day 23, whereas lipase and chymotrypsin releases were increased. If, however, secretion is expressed in percentages of the amount of enzyme released over the total tissue content, the output of the three enzymes in response to urecholine is significantly reduced from day 25 in pups kept on maternal milk only. These results suggest that dietary fat and carbohydrate modulate the enzyme content of the pancreas and that milk as the only source of energy and protein reduces the pancreatic acinar cell responsiveness to urecholine.