STIMULATION OF APICAL H-K-ATPASE IN INTERCALATED CELLS OF CORTICAL COLLECTING DUCT WITH CHRONIC METABOLIC-ACIDOSIS

This study evaluated the role of H-K-adenosinetriphosphatase (H-K-ATPa se) with chronic metabolic acidosis (CMA) in intercalated cells (ICs) of rabbit cortical collecting duct (CCD). CMA was induced by replacing drinking water with 75 mM NH4Cl in 5% sucrose for 10-14 days. CCDs is olated from CMA and control rabbits were split open and exposed to the intracellular pH (pH(i)) indicator 2',7'-bis(carboxyethyl)-5(6)-carbo xyfluorescein. In N-2-hydroxyethylpiperazine-N' -2-ethanesulfonic acid -buffered solutions, the resting pH(i) in ICs was similar for both gro ups. K-dependent pH(i) recovery (5 mM K, 140 mM N-methyl-D-glucamine) was monitored in response to a pulse of NH4Cl (10 mM). The K-dependent pH(i) recovery rate was threefold higher in CMA ICs compared with con trols and was abolished with the gastric H-K-ATPase inhibitor, Sch-280 80 (10(-5) M). Polarity of the H-K-ATPase was studied in microperfused CMA and control CCDs. Luminal K-dependent pH(i) recovery was monitore d in response to an acute pulse of NH4Cl in individual peanut lectin a gglutinin (PNA)-binding ICs. The apical Sch-28080-inhibitable K-depend ent pH(i) recovery rate was significantly greater in CMA ICs than cont rol ICs. In summary, CMA enhances functional activity of an apical H-K -ATPase in PNA-binding ICs of rabbit CCD.