Characterization of acid-base transport mechanisms in the kidney cell line RCCT-28A

RCCT-28A cells, a continuous cell line of rabbit cortical collecting tubule origin, have been found to exhibit apical peanut-lectin binding, basal band-3 immunostaining and a transepithelial electrical resistance of 246 +/- 37 omega cm2. For the studies reported, confluent monolayers of RCCT-28A cells were grown on permeable wells and incubated in a control solution or in alkaline solutions by lowering PCO2. Equivalent H+ fluxes (JH+) into the apical solution (nmol.min-1.cm2) were measured in the absence of drugs and in the presence of: amiloride (A, 10(-3) M), N-ethylmaleimide (NEM, 5 mM) and omeprazole (OM, 100 microM) in the apical solution. After preincubation in control solutions JH+ was 21 +/- 2 while A had no effect. Addition of NEM diminished JH+ to 12 +/- 2 (P < 0.005), and OM diminished JH+ to 2 +/- 2 (P < 0.001 vs. control). Monolayers incubated at low PCO2 had a basal JH+ of 11 +/- 5. No effect on JH+ could be demonstrated under these conditions by addition of NEM or OM. Removal of K+ from the apical solution diminished apical acidification by 60%. The inhibitor of H+,K(+)-ATPase Schering 28080 (SCH) was tested at different concentrations and an inhibitory effect was demonstrated (JH+ -2 +/- 1 vs. 18 +/- 1, SCH vs. control, respectively). Probenecid and bafilomycin-A also decreased apical acidification and an apical base-equivalent extrusion was apparent under the inhibitors effect. JH+ was abolished by removal of Cl- from the basolateral solution.(ABSTRACT TRUNCATED AT 250 WORDS)