In Vitro Aspects of Erythropoietin Production

Abstract

Erythropoietin (Ep) is a hormone active in the regulation of erythropoiesis; it is believed to be produced mainly in the kidney of adult animals and man.^1–3 Jacobson et al.¹ postulated the kidney to be the sole source of erythropoietin and Naets² substantiated Jacobson’s findings in the dog. While the kidney plays a major role as a site for erythropoietin production or activation in the adult, the question arises: where in the kidney is erythropoietin produced and are there extrarenal sites for Ep? Fisher et al.⁴ and Frenkel et al.⁵ using a fluorescent antibody technique, localized erythropoietin in the glomerular tuft of anemic sheep kidneys. Busuttil et al.^6,7 reported localization of erythropoietin in the epithelial cells of the glomerulus in anemic human kidneys and hypoxic dog kidneys. In addition, Gruber et al.⁸ using indirect immunofluorescent staining for erythropoietin, found fluorescent staining of glomerular cells in the kidneys of hypoxic adult rats (Figure 28-1) whereas no staining was seen in the kidneys of rats 1 or 2 weeks of age. This fluorescent staining was correlated with results of erythropoietin bioassay indicating that the kidney was not involved in erythropoietin elaboration at 1 or 2 weeks of age (Figure 28-2). While this study offers some credence to the use of immunofluorescence techniques, it is still debatable whether the glomerulus is a site of erythropoietin production or storage.