INFLUENCE OF ARTERIAL PO2 ON RENAL TISSUE PO2

When arterial PO2 is increased to supra‐atmospheric tensions approximating 500 mm Hg in the dog, the PO2 of the renal cortex rises from under 50 mm Hg to the range of 130 mm Hg, in contrast with that of the outer medulla which may even fall; there is little absolute change in the already extremely low PO2 of the inner medulla. These observations are interpreted to support the idea of a homeostatic mechanism operating to regulate medullary blood flow as already suggested by observations of urine PO2 at various arterial O2 tensions. This mechanism helps to maintain the hypoxic state of the medulla appropriate to its relatively anaeroboic metabolism. © 1969 Scandinavian Physiological Society