Effect of Thyroxine and Propylthiouracil on Magnesium Metabolism in the Rabbit. Study with Mg28.

Abstract

Rabbits were given thyroxine or propylthiouracil and external balance studies for Mg were performed. Mg28 was used to measure exchangeable body content of Mg. In 8 rabbits given 2 intravenous injections of thyroxine sodium (0.3 mg/kg) no significant changes were noted in body weight, Mg balance, or exchangeable Mg content, although a decrease in serum Mg concentration occurred. In another group of 8 rabbits the tissue relative activity of Mg28 was determined following 3 intravenous injections of thyroxine (1.0 mg/kg) given within 4 days. The relative activity was increased in liver, skin, appendix, and heart. Eight rabbits given propylthiouracil orally showed a decrease in exchangeable body content of Mg at the end of the 3rd week. A significant decrease was also found in relative radioactivity of liver and bone. The value for exchangeable body content of Mg appears related to the rate of turnover of Mg28 in bone and muscle, the two largest body stores of Mg.