THYROID HORMONE TREATMENT AND OXYGEN CONSUMPTION IN EMBRYOS OF THE SPINY DOGFISH

¹ Department of Zoology. Oregon State College, Corvallis, Oregon, and the Department of Zoology, Columbia University, New York 27, N. Y.

1. The oxygen consumption rate of "near-term" pups of the dogfish, Squalus suckleyi, was determined at regular intervals during the course of repeated injections of physiological saline solution, thyroid hormones, or of anti-thyroid substances. Up to 10 injections were given on alternate days.

2. Of the compounds tested, triiodothyroacetic acid at a dosage level of 10 micrograms per injection was the most consistent in raising the level of oxygen consumption. The effect, however, was transitory with oxygen consumption rising to a maximum (17% to 33%) level above the saline-injected controls after four injections, thereafter declining slowly to control levels.

3. L-thyroxine at a dosage level of 10 micrograms had a variable effect on oxygen consumption. In two of four experiments the oxygen consumption rate rose irregularly, reaching a level about 20% above the controls after 9-10 injections. In the remaining experiments, there was no clear tendency to remain above the controls.

4. Propylthiouracil, after 9 injections, had no consistent effect on metabolic rate in four experiments.

5. The results are discussed with reference to the possible level of thyroid function in these animals.