II. Effect of Thyroidectomy and Suprarenalectomy on Muscle Tissue Respiration.

Abstract

In a previous paper 1 it was shown that suprarenalectomy increased the respiration of excised abdominal muscle of mice. This increase was shown to obtain only from about the fifty-fifth to the seventieth day after suprarenalectomy. Further experimentation has shown that this period probably begins nearer the fiftieth day so that in this paper comparisons are made for a period extending from about the fiftieth to the seventieth day after suprarenalectomy. To determine the rôle of the thyroids in this increased respiration a series of mice was first thyroidectomized and then about 3 weeks later suprarenalectomized. The operated mice were kept on a bread and buttermilk diet about 6 weeks, 3 weeks before and 3 weeks after thyroidectomy. After this period the diet was changed to dry bread and grains, the buttermilk being retained as the only drink allowed. The control litter mates received similar treatment. After thyroidectomy the operated mice received subcutaneous injections of one-tenth of a milligram of thyroxin∗ solution 3 times weekly. The respiration of the excised abdominal muscle of both normal and operated mice (50 to 70 days after suprarenalectomy) was measured using the same technique as reported previously, namely, a modification of the Warburg differential method.

The respiration values obtained in 13 such experiments are shown in Table I which is self-explanatory and similar to Table I of the previous paper. 1 It will be remembered that the last 4 columns express the quantity of lactic acid produced both aerobically and an-aerobically in accordance with the Warburg method in terms of cubic millimeters of carbon dioxide produced during the first hour of respiration per milligram of dried tissue.