Previous studies have suggested the presence of an H(+)-K(+)-
ATPase in rat cortical and medullary intercalated cells with similar properties to the gastric
proton pump. The purpose of this study was to determine the functional contribution of an H(+)-K(+)-
adenosinetriphosphatase(
ATPase) to total CO2 (
tCO2) transport along the rat collecting duct. After baseline determination of
tCO2 transport in isolated perfused collecting duct segments,
Sch 28080 (10 microM) was added to either the perfusate or bath. When
Sch 28080 was added to the perfusate, there was no effect in the cortical collecting duct (CCD, 20.8 +/- 6.7 vs. 25.3 + 3.0 pmol.mm-1.min-1), but a marked decrease in
tCO2 absorption was effected in both the outer medullary (OMCD, 37.6 + 6.2 vs. 10.7 +/- 4.1 pmol.mm-1.min-1) and initial inner medullary collecting duct (IMCD1, 34.4 +/- 8.1 vs. 16.2 +/- 5.6 pmol.mm-1.min-1). In the CCD from rats with acute
alkalosis in vivo,
Sch 28080 added to the bath inhibited
tCO2 secretion in the CCD (-17.1 +/- 4.4 vs 3.5 + 3.3 pmol.mm-1.min-1). These findings suggest that 1) H(+)-K(+)-
ATPase is important in
tCO2 absorption in the OMCD and IMCD1 and in
tCO2 secretion in the CCD, 2) HCO3(-)-absorbing intercalated cells differ functionally in the cortex and medulla, 3) HCO3- secretion is not the reverse process of HCO3- absorption in the CCD, and 4) H(+)-K(+)-
ATPase is important in distal acidification under normal and altered
acid-base conditions.