Tissue Respiration and Endocrine Function. III. Influence of Thyroidectomy on Tissue Respiration. ∗

Abstract

Opinion differs in regard to the exact method by which the thyroid hormone exerts its influence on body metabolism. Plummer and Boothby, 1 Kendall 2 and others have accepted the view that its action is within the cells themselves and believe that it acts as a catalyst. Kunde 3 has shown that when daily repeated doses of thyroid substance are given to dogs a progressive increase in metabolism occurs as time advances, reaching a maximum in 3 weeks or more after the initial dose. This investigator states further that the height of response to a quantity of the thyroid substance depends upon some condition of the body cells, which become less and less resistant to repeated doses of the thyroid hormone, and that the catalytic theory of Plummer is inadequate to explain hyperthyroidism experimentally induced in dogs.

Data previously reported from this laboratory 4 would indicate that the apparent catalysis of the fundamental processes of metabolism induced by thyroid substance is, in part at least, indirect, i. e., that it exerts its influence upon the body cells by increasing the amount, potency or some other property of the oxidation catalysts normally present. As measured by the indophenol oxidase activity, there is a diminution of from 10 to 50% in the respiratory power of the cells from tissues of cretin pups and lambs.

The present experiments were undertaken to determine the oxygen consumption of surviving tissues from cretin pups (thyroidecto-mized when 5 weeks of age, tissues studied 7 months later) as compared with their normal litter-mates of the same sex. If the diminished metabolic rate of the thyroidectomized animal is reflected in the surviving tissue, it follows that normally the thyroid hormone must accumulate in the cells, if its action is to be considered as catalytic in nature, or that it must affect, in some way, one or more of the normal constituents of the cells. Foster 5 reported a diminution of from 25 to 30% in the oxygen consumption of surviving strips of diaphragm muscle from thyroidless rats.