PRODUCTION OF POLYCYTHEMIA IN HYPOPHYSECTOMIZED RATS BY THE PITUITARY ERYTHROPOIETIC FACTOR1

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Abstract
Injection of the pituitary erythropoietic factor in hypophysectomized rats resulted in the development of polycythemia. The rats were females of the Long-Evans strain, hypophysectomized when 26-28 days of age and maintained for at least a 45 day postoperative period in order to allow for development of the characteristic post-hypophysectomy anemia. Daily subcutaneous injection of 0.100 mg of the erythropoietic factor for 14 days not only repaired the anemia, but resulted in hematological values (hemoglobin, hematocrit and total red cell volume) exceeding those of the normal controls. Since none of the known pituitary tropic hormones, even when given at high levels over a long period, has been able to achieve this result, the production of polycythemia in hypophysectomized rats was interpreted as giving additional support to the concept that the pituitary erythropoietic factor is a substance distinct from all other hypophyseal hormones.