Hormonal Control of Erythropoiesis in Canine Cyclic Haematopoiesis

Abstract

The results of erythropoietin (ESF) studies in dogs with cyclic hematopoiesis are presented. Even though the dogs were exposed to a constant stimulus of hypoxia, cycles in the plasma ESF levels occurred at 11-12 day intervals. In some dogs, minor midcycle peaks were observed and the amount of ESF produced varied with the different animals. The peaks of ESF characteristically appeared approximately 5 days after the onset of neutropenia. A hypothesis is presented to explain the known facts concerning canine cyclic hematopoiesis. A poietin controlling factor may be produced and this assumed factor apparently then stimulates the production of specific factors leading to increases of reticulocytes, platelets and monocytes. The monocytes in turn produce more colony stimulating factor (CSF) leading to the formation of granulocytes. Such a sequence of events would explain the apogee of reticulocyte, platelet and monocyte counts at a time when the nadir of granulocyte counts is reached.