The Effect of Propylthiouracil on Exocrine Glands

This study was designed to compare the effect of hypothyroidism on the submaxillary gland with that on other exocrine glands. Weights and enzymatic activity of submaxillary gland, parotid gland and pancreas were determined at 30, 60 and 90 day intervals in a control group of rats fed ad libitum, an experimental group fed ad libitum and receiving .075% propylthiouracil in their drinking water, and a pair-fed group. Rats on propylthiouracil reduced their food intake by about 23-30%. The pair-fed group showed that this degree of restriction of food intake: 1) resulted in an increase in the relative weights of the submaxillary gland and of the pancreas, 2) caused a significant decrease in the specific protease activity of the submaxillary gland, but did not affect the specific protease activity of the pancreas, and 3) had no effect on the specific amylase activity of the pancreas or parotid. After discounting these effects of reduced food intake in the experimental animals, it was concluded that propylthiouracil: 1) decreased the absolute weights and the organ/body weight ratios of the submaxillary gland and of the pancreas, 2) depressed the specific amylase activity of the pancreas and of the parotid gland, and 3) had no effect on the specific protease activity of the submaxillary gland and that of the pancreas. No differential effect of the drug on the submaxillary glands were observable. The action of the thyroid hormone thus appears to differ from that of the male sex hormone, which interferes specifically with the proteolytic activity of the salivary gland.