Hydrogen ion secretion by the collecting duct as a determinant of the urine to blood PCO2 gradient in alkaline urine
Several theories have been advanced to explain the elevation in urinary PCO/sub 2/ during bicarbonate loading and include: (a) H+ secretion, (b) countercurrent system for CO/sub 2/, (c) the ampholyte properties of bicarbonate, and (d) mixing of urine of disparate bicarbonate and butter concentrations. In this study microelectrodes were used to measure in situ and equilibrium pH (pHis and pHeq) and PCO/sub 2/ in control and bicarbonate loaded rats before and after infusion of carbonic anhydrase. The disequilibrium pH method (pHdq . pHis - pHeq) was used to demonstrate H+ secretion. Control rats excreting an acid urine (pH . 6.04 +/- 0.06) failed to display a significant disequilibrium pH at the base (BCD), or tip (TCD) of the papillary collecting duct. Urine pH (7.54 +/- 0.12), and urine to blood (U-B) PCO/sub 2/ increased significantly during NaHCO/sub 3/ loading while PCO/sub 2/ at the BCD and TCD also increased (95 +/- 4 and 122 +/- 4). Furthermore, an acid disequilibrium pH was present at both the BCD and TCD (-0.42 +/- 0.04 and -0.36 +/- 0.03) and was obliterated by carbonic anhydrase. Comparison of the PCO/sub 2/ in the BCD or TCD with the adjacent vasa recta revealed similar values (r . 0.97). It is concluded that H+ secretion by the collecting duct into bicarbonate containing fluid with delayed dehydration of H/sub 2/CO/sub 3/, is the most likely determinant of the U-B PCO/sub 2/ in alkaline urine. Similar values for PCO/sub 2/ in the collecting duct and the adjacent vasa recta suggests trapping of CO/sub 2/ in the medullary countercurrent system. The rise in PCO/sub 2/ occurs both along the collecting duct and after exit from the papilla.
- Research Organization:
- Department of Internal Medicine, University of Texas Health Science Center at Dallas
- OSTI ID:
- 5451667
- Journal Information:
- J. Clin. Invest.; (United States), Vol. 69:1
- Country of Publication:
- United States
- Language:
- English
Similar Records
ENHANCEMENT OF THE RENAL EXCRETION OF CESIUM-137 IN RATS TREATED WITH ACETAZOLAMIDE AND RELATED COMPOUNDS
Surfactant secretion is stimulated by decreased alveolar CO/sub 2/
Related Subjects
URINE
BIOCHEMICAL REACTION KINETICS
ACID CARBONATES
CARBON DIOXIDE
CARBONIC ANHYDRASE
HYDROGEN IONS 1 PLUS
PH VALUE
RATS
ANIMALS
BIOLOGICAL MATERIALS
BIOLOGICAL WASTES
BODY FLUIDS
CARBON COMPOUNDS
CARBON OXIDES
CARBON-OXYGEN LYASES
CATIONS
CHALCOGENIDES
CHARGED PARTICLES
ENZYMES
HYDRO-LYASES
HYDROGEN IONS
IONS
KINETICS
LYASES
MAMMALS
MATERIALS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
RODENTS
VERTEBRATES
WASTES
550200* - Biochemistry
551000 - Physiological Systems