Properties permitting the renal cortex to be the oxygen sensor for the release of erythropoietin: Clinical implications

The Po-2 at this site where erythropoietin release is regulated should vary only when the hemoglobin concentration changes in capillary blood. The kidney cortex is an ideal location for this O-2 sensor for four reasons. First, it extracts a small proportion of the oxygen that is delivered in each liter of blood; this makes the Po-2 signal easier to recognize. Second, there is a constant ratio of the work performed (consumption of O-2) to the renal blood flow rate (delivery of O-2). Third, the high renal blood flow rate improves diffusion of O-2 from capillaries to this O-2 receptor. Fourth, a high renal cortical Pco(2) prevents an additional shift of the O-2:hemoglobin dissociation curve by other factors from being a confounding variable. This suggests that the GFR and the renal blood flow rate should be examined in patients with unexplained anemia or erythrocytosis.