Extraction of erythropoietin from kidneys.

Erythropoietin (Ep) in large amounts was detected in extracts of renal tissue from hypoxic rats. These extractions were performed by homogenization of kidney tissue in phosphate buffered saline, centrifugation at 3,000 g and collection of the supernate. Male kidneys contained more Ep than did females and the major portion of Ep is located in the renal cortex. Comparison of intrarenal and plasma Ep levels at various times following initiation and cessation of hypoxia appears to be a useful method for studying the kinetics of erythropoietin production and release, and also for studying feedback mechanisms that influence these functions.