Study of Humoral Factors Regulating the Production of Leukocytes. I. Demonstration of a "Neutropoietin" in the Plasma after Administration of Triamcinolone to Rats

Male Wistar rats were divided into 3 groups: Group I. Rats given the triamcinolone daily by gastric catheter all developed neutrophilia accompanied by lymphopenia. Group II. Rats given daily intraperitoneal injections of plasma from normal rats manifested no significant alteration in the peripheral blood elements. Group III. Rats given daily intraperitoneal injections of plasma from rats given triamcinolone invariably developed neutrophilia without lymphopenia. Studies of the bone marrow of these groups at the end of the experiments revealed increased myeloid:erythroid ratios in Groups I and III but not II. It is therefore believed that this experiment suggests the existence of a neutrophilia-promoting factor in the plasma following the administration of triamcinolone.