Erythropoietic Response to Calorigenic Hormones1

Experimental evidence is presented which demonstrates that a parallel exists between the effectiveness of corticotrophic pituitary preparations in restoring to normal heat production (oxygen consumption) and erythropoiesis (red cell volume) in hypophysectomized rats. Both effects are absent when the adrenals are also removed. Oxidation of the N-terminal serine of corticotrophin by periodate destroys both responses. The adrenal glucocorticoids exert both effects in hypophysectomized rats and as with corticotrophin the responses increase with dose. In the absence of the thyroid as well as the pituitary the erythropoietic response to adrenal steroids is marginal, judged by calculations based on final body weight, but negative judged on the basis of initial body weight, the difference being due to serious weight loss. Thyroidectomized rats also display a weight loss after adrenal steroid administration which complicates the interpretation of the erythropoietic values. Surprisingly, there is a striking regranulation of pituitary acidophils in thyroidectomized rats treated with hydrocortisone. Thyroxine in normal rats induces excess heat production, without detriment to body size, and polycythemia accompanied by adrenal cortical hypertrophy. The plasma of such polycythemic animals does not contain an erythropoietic stimulant. Thyroxine in hypophysectomized rats increases heat production and restores erythropoiesis to normal, but not above normal, with no adrenal cortical response. Dinitrophenol, another potent calorigenic agent, also increases red cell volume in the thyroid deficient animal. These findings re-emphasize the crucial role of the endocrine system in adjusting the erythrocyte content of the blood to the oxygen requirements of the organism.