Mechanism of regulation of renal bicarbonate reabsorption by plasma CO₂ tension

¹ Department of Medicine, Harvard Medical School, and Peter Bent Brigham Hospital, Boston, Massachusetts

It is known that the capacity of the kidney for bicarbonate reabsorption is a function of the systemic arterial pCO₂. This relationship could be due to a direct effect of the level of arterial pCO₂ on the kidney, or could be mediated by an extrarenal hormone. A surgical preparation has been devised in the dog whereby the pCO₂ of the blood supplying the left kidney can be increased directly without significantly raising the pCO₂ of the rest of the systemic arterial blood. It was found that a selective increase in left renal arterial pCO₂ led to a rise in Tm_hcohco3 of the left kidney. This rise in Tm_hcohco3 was 73% of that produced by an equivalent elevation in the pCO₂ of the whole systemic arterial system. It is concluded that the relationship between systemic arterial pCO₂ and renal bicarbonate reabsorption is due in large measure to a direct effect of the level of arterial pCO₂ on the kidney.

Key Words: renal reabsorption of bicarbonate • bicarbonate Tm plasma tension of carbon dioxide • kidney • pCO₂ of plasma • urine bicarbonate

Submitted on November 1, 1963