Mechanism by which neutral phosphate infusion elevates urine Pco2

Bobby J. Stinebaugh, Francis X. Schloeder, Elias Gharafry, Wadi N. Suki, Marc B. Goldstein, Mitchell L. Halperin

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


Currently, the ability to elevate the urine Pco2 above that of the arterial blood is employed as an estimate of distal hydrogen ion secretion. Therefore, it is important to establish the mechanisms by which various factors affect the urine CO2 tension. This paper examines the physiologic process by which phosphate elevates the urine Pco2 in the dog. The rise in urine Pco2 due to phosphate could be the result of either (1) a distal mechanism, by affecting the delayed dehydration of carbonic acid, or (2) an increase in the medullary Pco2. The phosphate-induced elevation of urine Pco2 was abolished by carbonic anhydrase infusion. This indicates that a distal mechanism is a major factor in the phosphate effect. Since acid phosphate infusion did not result in an elevated urine Pco2, it is unlikely that changes in the medullary Pco2 occur as a result of phosphate infusion. The rise in urine Pco2 due to phosphate was accompanied by an increase in net acid excretion, indicating an increase in hydrogen ion secretion. The increased hydrogen ion secretion and rise in urine Pco2 were reproduced by infusion of the buffer, Tris-(hydroxymethyl)-aminomethane, but not by sodium sulfate administration. These findings suggest that the phosphate-induced rise in urine Pco2 is due to the buffer properties of phosphate rather than to its nonreabsorbable anion characteristics.

Original languageEnglish (US)
Pages (from-to)946-958
Number of pages13
JournalThe Journal of Laboratory and Clinical Medicine
Issue number5
StatePublished - Jan 1 1977

ASJC Scopus subject areas

  • Pathology and Forensic Medicine


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