Effect of Protein-Energy Malnutrition and of a Powdered Diet on the Parotid Gland and Pancreas of Young Rats

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Abstract
In order to determine if parotid gland enlargement is associated with malnutrition in rats as has been frequently reported for humans, young rats were either fed a standard pelleted laboratory stock diet or were fed a protein-adequate, but powdered, diet for 1 week and then the diet of half of these rats was switched to a powdered diet of low protein content (0.5% lactalbumin). The parotid glands of those fed the pelleted diet for the duration of the study increased 46% in DNA, 150% to 200% in weight, RNA and protein, and 285% in amylase; those fed the protein-adequate powdered diet showed no change in DNA content, increased only 100% in weight and amylase, 76% in protein and 23% in RNA. Body weight changes were similar for both of these groups. Those fed the low protein diet showed a 40% to 50% decrease in body weight during the 10 weeks of the study. Parotid gland weight, DNA, RNA and protein content were decreased by 20% to 40% and amylase by 72%. At no point was a gland enlargement found. Since the pancreas is profoundly affected by malnutrition, it was also studied. The changes in this organ were more severe with reductions of 70% to 80% in weight, protein, DNA and RNA content and 96% in amylase. The results confirm that growth of the rat parotid gland is sensitive to diet consistency and to mastication, and indicate that parotid gland enlargement is not associated with malnutrition in young rats.