Abstract
The direct-assay of cobalt and sheep erythropoietin in the nephrectomized rat revealed that removal of the kidneys reduced the erythropoietic response to cobalt but did not modify significantly the response to sheep erythropoietin. Neither sham operation nor peritoneal dialysis was observed to exert a significant influence on radioactive iron incorporation in the starved rat. A moderate elevation in plasma BUN occurred in tile dialyzed nephrectomized rats but did not modify the capacity of the nephrectomized rat to respond to erythropoietin. No significant change occurred in plasma potassium in the lavaged-nephrectomized rats. Bilateral nephrectomy was found to result in a significant reduction in total circulating red cell and blood volume. Plasma iron was significantly reduced by both nephrectomy and cobalt administration, but was not significantly influenced by sheep erythropoietin. The findings reported in these studies, as well as those of other workers, leaves little doubt that the kidney plays an "active" role in erythropoiesis. The existence of a "permissive" renal erythropoietic factor does not seem likely.
