Renal biogenesis of erythropoietin.

The widespread and ever expanding use of dialysis in the maintenance of patients with chronic renal disease has added an urgency to the study of the biogenesis of erythropoietin. It seems almost certain that erythropoietin could ameliorate, if not eliminate, the anemia of uremia, but unfortunately, erythropoietin is still not available in therapeutic quantities. Initially, erythropietin was though to be produced by the kidneys" but then the attention became directed at the liver. It was proposed that erythropoietin was produced there as an inactive precursor and that the kidney only acted as an oxygen sensor and as a producer of an erythropoietin-activating enzyme. Recent studies summarized here show that an isolated perfused kidney in the absence of any extrarenal substrate or precursor can synthesize erythropoietin. Consequently, it appears almost certain that the kidney is the endocrine organ of origin of erythropoietin. Further studies suggest that erythropoietin formation involves a phase of oxygen sensing and programming and a phase of synthesis. These phases probably occur in the same cell, and the renal cortex appears to be the most likely location for such cells. The current inability to extract erythropoietin from kidney homogenates is discussed but, unfortunately, not adequately explained.