Comparative studies of the age-related changes in protein synthesis in the rat pancreas and parotid gland

Abstract

This study was undertaken to determine whether changes occur in protein synthesis with age in the pancreas of the rat and to compare the pattern of changes with that observed in parotid salivary glands. The rate of incorporation of 3H-leucine into acid-insoluble proteins declines with age in both glands. In the pancreas, the rate of incorporation reaches the highest level at 12 months and declines by 21, 54 and 64% of this level at 18, 24 and 30 months, respectively. In parotid glands, the highest level of the amino acid incorporation occurs at 2 months and the level declines by 21, 29, 49 and 58% of the 2-month level at 12, 18, 24 and 30 months, respectively. There is no age-related difference in the rate of incorporation of 3H-leucine into acid-soluble fractions of the two glands. The cellular level of [alpha]-amylase is also reduced in the pancreas and parotid gland of old (24- and 30-month-old) rats. The differences in the cellular level of [alpha]-amylase activity among the age groups correlate with the differences in the number of secretory granules present in the acinar cells of the pancreas, indicating that the level of amylase reflects the cellular content of secretory proteins. There is no detectable morphological change that parallels the over 50% reduction in protein synthesis in these glands of young and old rats.