Effect of moderate chronic protein deficiency on rat salivary components.

Chronic protein insufficiency was achieved in rats with an 8% protein diet initiated at weaning. The total activity and activity per milliliter of the principal salivary protein, amylase, were significantly decreased at day 66. The amount of total protein per milliliter of saliva and total protein in stimulated saliva collected during 30 minutes was decreased in the malnourished rats. The levels of immunoglobulin G (IgG) and aminopeptidase in saliva were not affected by dietary status. Prolonged malnutrition on the low-protein, high-starch diet resulted in an apparent stimulation or induction of salivary amylase and protein secretion by day 110. Total protein collected and milligram of protein per milliliter of saliva were very similar in the malnourished and control rats at day 110. Salivary amylase activity in the malnourished rats was significantly greater than in the saliva of controls. The initial decrease in the principal salivary protein, amylase, and in total protein followed by a significant increase with prolonged stimulation by low-protein and high-starch diets suggests that early protein deficiency retards synthesis of amylase and that a high-starch diet may induce salivary amylase production.