Implications of urine pO₂ for renal medullary blood flow

¹ Department of Pathology, Yale University School of Medicine, New Haven, Connecticut

The pO₂ of ureteral urine under osmotic diuresis responds inversely to changes in renal arterial and venous pO₂. With a rise in arterial pO₂ there is only a transient increase but then a rapid fall in urinary pO₂, usually to lower than the initial levels in both anesthetized and unanesthetized dogs. Opposite changes occur when the arterial pO₂ is diminished. The renal blood flow falls as arterial pO₂ rises with transfer of the animal from air to 100% O₂, but the total O₂ consumption of the kidney remains unaltered. The most simple and reasonable explanation of these findings postulates the existence of a mechanism sensitive to arterial pO₂ for redistribution of medullary blood flow. This does not, however, rule out the possibility that an increase in arterial pO₂ might be accompanied by an augmentation of O₂ utilization so large as to diminish tissue pO₂, and vice versa. If this is true there is, to our knowledge, no analogue in biology and there are several points of evidence against the metabolic hypothesis.

Key Words: urine oxygen tension • kidney, medulla, blood flow • hemodynamics, kidney, medulla

Submitted on December 31, 1962

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