Amylase mRNA synthesis and ageing in rat parotid glands following isoproterenol-stimulated secretion

Abstract

In the parotid, as well as in other exocrine glands, secretory protein synthesis declines with age. However, whether this decline in the steady-state rate of protein synthesis reflects the reduced digestive activity of the animal or actual cellular alterations that affect synthesis is unknown. Here the ability to synthesize amylase and its mRNA during the period of enhanced protein synthesis following secretion induced by isoproterenol was compared in acinar cells of 2-and 24-month-old rats. In unstimulated glands, rates of synthesis of total protein and amylase, as well as amounts of amylase mRNA, were significantly less in the older rats than in their younger counterparts. After stimulation with isoproterenol, which induced the secretion of about 50% of stored proteins, rates of synthesis of total protein, as well as amylase, were increased by about 2.5 x the unstimulated rates in both age groups. However, the amount of amylase mRNA did not increase in parallel with the increase in the rate of amylase protein synthesis in both young and old rats. The molecular size of the mRNA was the same in stimulated and unstimulated glands of both age groups. Thus, it appears that parotid acinar cells from old rats can be stimulated to synthesize secretory proteins at an increased rate. It remains to be determined what causes the reduced rate of protein synthesis in unstimulated glands in old rats.

Temporal response pattern of biochemical analytes in experimental diabetes

“…In Figure 4, the rise in seric AMS activity (principally of salivary and pancreatic origin) between day 11 and day 40 after administration of saline, in group N, may be related to fluctuations in the rates of synthesis and secretion of the secretory glands. Such fluctuations have been attributed to aging of the animals [33–36]. The fall in AMS serum activity (Figure 4) corroborates the data of Barneo et al [3], who observed the same in diabetic animals and proposed a correlation with the severe insulin debt found in diabetes type 1, since this fall was not seen in type 2 cases [3].…”

Quantitative subproteomic analysis of age-related changes in mouse liver peroxisomes by iTRAQ LC–MS/MS

“…This enzyme with predicted lysosomal localization, catalyzes the cleavage of alpha-1,4-glucosidic linkages between glucose molecules in starch, and thus plays an important role in starch digestion. It has been shown for parotid and other exocrine glands that synthesis of secretory proteins, especially alpha-amylases, declines with age, and the salivary function in general decreases [36]. This observation would explain significant decrease of alpha-amylase level in old mouse liver that we observe in our study.…”

Evaluation of toxicity after one-months treatment with Bauhinia forficata decoction in streptozotocin-induced diabetic rats

“…In the present study we detected only a tendency for serum amylase activities to be lower in diabetic than normal rats throughout the experiment, such changes possibly being due to endocrine, exocrine and paracrine changes in the parenchyma of the pancreas [19,26,27]. In both normal groups the increased amylase activity observed during the experiment may have been related to fluctuations in the rates of amylase synthesis and its secretion by secretory glands, such fluctuations having been attributed to ageing of the animals [28-31]. The significant increase in amylase activity in the diabetic-treated group on day 33 relative to time zero does not necessarily indicate toxicity because there was no significant difference between the amylase activities of the diabetic-treated and diabetic-control groups on day 33, and it appears that the rise in amylase level in the diabetic-treated group on day 33 is probably due to a random effect.…”