Abstract
Summary and Conclusions
1. Following hypophysectomy of rats, reticulocytes in the peripheral blood fall to a minimal level within a period of 3 to 4 weeks. This reduction represents a 5- to 10-fold decrease from the prehypophysectomy control. This reticulocyte decline is more rapid in 8-week-old rats than in younger animals. 2. Administration of anemic plasma to hypophysectomized rats produces a reticulocyte rise that is many fold greater than that produced by normal plasma or saline. 3. Erythropoiesis, as measured by the number of reticulocytes in peripheral blood, falls to zero in 6 days in mice made polycythemic by repeated intraperitoneal injections of homologous red cells. Anemic plasma obtained from rats or rabbits, when injected intravenously or intra-peritoneally into polycythemic mice, produces a reticulocytosis many times greater than that observed from normal plasma. Normal saline produces no increase in reticulocytes. 4. In polycythemic mice and hypophysectomized rats, reticulocyte determinations in the peripheral blood and Fe59 red cell incorporation studies are of about equal sensitivity in measuring the response to anemic plasma.
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