Premature Increases in Amylase of Postnatal Rat Parotid with Chronic Isoproterenol 1

Abstract

Summary

Chronic administration of large doses of isoproterenol during postnatal development caused an increase in amy-lase levels of parotid gland of the immature rat. The magnitude of the increase and the cellular basis for amylase changes depended on the postnatal period during which isoproterenol was given. If given during a pre-weanling period (9-17 days of age), total amylase as well as gland and cell size and total RNA were twice the levels of control litter-mates; the amount of amylase per unit of cytoplasm or per microgram of RNA was unchanged from levels of controls but the amount per microgram of DNA was nearly three times that of controls. If given during a postweanling period (23-31 days of age), the increase in total amylase corresponded to the increase in total DNA (about 50% increase in each when compared with controls), but the amount per unit of DNA was unchanged from controls, and the amount per milligram tissue wet weight or microgram of RNA was in fact only one-third the control levels. In the preweanling rat, the ability of the parotid to produce amylase keeps pace with the increase in cytoplasm in the preweanling rat but not in the postwean-ling rat. The increases in amylase in the preweanling gland are interpreted as evidence of an acceleration of functional development (increased accumulation of amylase), but in postweanling rats the increases in amylase do not provide unequivocal evidence for accelerated development.