Article révisé par les pairs
Résumé : All levels of digestive enzymes did not change in constant proportion in the rat pancreas before weaning, and different stimuli were probably responsible for their emergence. The high levels of amylase and chymotrypsinogen observed during the late fetal period were followed by a marked depression in the newborn period. Prompt administration of hydrocortisone prevented the drop of these hydrolases and enhanced the low activity of trypsinogens in 1 to 23 day old pups. This observation together with the reported decreasing activity of the pituitary adrenal axis during the first neonatal weeks suggests that glucocorticoid secretion is a stimulus effective in evoking a series of pancreatic hydrolases. On the other hand, the emergence of lipase was slow, responding poorly to hydrocortisone and to nutritional controls only after 25 days. L Thyroxine, glucagon, or dibutyryl cyclic AMP was unable to increase the specific activities of all hydrolases tested. Nutritional controls were predominant in regulating levels of hydrolases in adult rats. The time course of variation in specific activities of amylase and lipase on high corn oil and high starch diets was unaffected by 7 days of glucagon administration. Adrenalectomy tended to decrease and hydrocortisone treatment tended to increase the level of pancreatic amylase in rats submitted to the same dietary manipulations. The accumulation of amylase required the presence not only of starch but also of protein in the diet.