Estimation of Thyroxine Output by the Thyroid Glands of Normal and Adrenalectomized Rats by Means of a Simple Cooling Test
SCHOOL OF AVIATION MEDICINE RANDOLPH AFB TX
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Adrenalectomy, administration of propylthiouracil, or a combination of these two treatments increased significantly the rate of cooling of rats restrained and subjected to air at 5C. Propylthiouracil administration increased rate of cooling 55 percent above that of untreated control rats while adrenalectomy increased rate of cooling 84 percent. The combination of these two treatments increased rate of cooling 99 percent. Dead rats cooled 201 percent faster than control rats. Administration of graded doses of thyroxine to both adrenalectomized-PTU-treated rats and to normal PTU-treated rats indicated that 1.9 and 4.4 gamma per day of thyroxine, respectively, were required to return rate of cooling to that of comparable controls. These doses are, therefore, the best estimates of thyroxine outputs by thyroids of these animals. The results suggest that adrenalectomy is accompanied by diminished thyroid function. This fact makes difficult any evaluation of the relative roles of thyroid gland and adrenal glands in the maintenance of body temperature of rats exposed to cold.
- Anatomy and Physiology