Premature Increases in Amylase of Postnatal Rat Parotid with Chronic Isoproterenol

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Abstract
Chronic administration of large doses of isoproterenol during postnatal development caused an increase in amylase 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 preweanling 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 .mu.g of RNA was unchanged from levels of controls but the amount per .mu.g of DNA was nearly 3 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 mg tissue wet weight or .mu.g of RNA was in fact only 1/3 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 postweanling 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. [These findings provide additional evidence of neural regulation of developmental changes in amylase levels of rat parotid.].