Perinatal changes in amylase and serum corticosterone levels in rats.

In rats amylase activity in the pancreas increased greatly from day 15 of gestation to a maximum on day 21. Then it decreased to less than one-tenth of this maximum value on about day 5 after birth. It increased again about 15 days after birth and reached the adult level about 30 days after birth. No amylase activity was in the parotid gland before birth: it appeared about 12 days after birth and reached the adult level, which was higher than that in the pancreas, about 30 days after birth. The serum corticosterone level was as high as the adult level before birth. Then it decreased to less than one-tenth of the adult level 5 days after birth and increased again from 15 to 25 days after birth to the adult level. The developmental change in the serum corticosterone level seemed to influence amylase activity in the pancreas both before and after birth, and that in the parotid gland only after birth. The serum contained both pancreatic and parotid type isozymes of amylase until 1 day after birth but only the parotid type from 3 days after birth.