INFLUENCE OF HYPOPHYSECTOMY ON THE HEMOPOIETIC RESPONSE OF RATS TO LOWERED BAROMETRIC PRESSURES1

Abstract

Subjection of hypophysectomized rats to reduced pressures of 411 mm. Hg (16,000 ft.), for periods up to 14 days, produces no significant effects upon the peripheral red blood cell values, Hb levels or bone marrow histology. Positive responses to these pressures are obtained in the unoperated controls. Pressures of 321 mm. Hg. (22,000 ft.), however, evoke in the hypophysectomized animal an erythropoietic response of approx. the same magnitude as that displayed by unoperated controls. Although the pituitary is essential for the erythropoietic response to moderately low pressures (411 mm. Hg), a full effect may be produced independently of this gland at more severe levels of anoxia.