Temporal transition in the site of rat erythropoietin production

Plasma erythropoietin levels have been determined in nephrectomized, hepatectomized, nephrectomized and hepatectomized, and intact hypoxic rats--1, 2, 3 and 8 weeks of age. The liver appears to be the primary site of erythropoietin production during the first 2 weeks of life. By the third week, the kidneys began producing erythropoietin and by 8 weeks, they were the major organs of erythropoietin production. Indirect immunofluorescent staining for erythropoietin of renal and hepatic tissue correlated with the results of the erythropoietin bioassay. Fluorescent staining of glomerular cells in the kidney and macrophages or Kupffer cells in the liver implicate these areas as possible specific sites of erythropoietin production.