CHARACTERIZATION OF PEANUT-LECTIN (+) CELLS DERIVED FROM THE RCCT-28A CELL-LINE

Cells from RCCT-28A cell line, which exhibited the highest peanut-lectin binding capacity [RCCT-28A(P+)] were separated and cultured attempting to obtain a population of HCO3- secreting cells. The mechanisms of apical solution acid or base extrusion were studied in confluent monolayers. In RCCT-28A (P+) cells net H+ flux (J(H)+, nmol . min-1 . cm-2) was significantly lower (J(H)+ = 13 +/- 3) than that observed in the RCCT-28A cells (21 +/- 2). N-ethylmaleimide, Bafilomycin-A, omeprazole and Schering 28080 decreased J(H)+ . Cl- removal from the basolateral side, in the presence or absence of SCH in the apical side, decreased J(H)+. Removal of apical Cl- abolished apical extrusion of base-equivalents. Incubation in a high bicarbonate solution results in base-equivalent flux to the apical side (J(H)+ = -7.0 +/- 1.0). Preincubation in a hyperosmotic medium (mannitol addition) at pH 7.5 decreased J(H)+ to -3.0 +/- 1.0. We conclude that, functionally, RCCT-28A(P+) cells are only quantitatively different from RCCT-28A cells. Acid secretion by these cells can be modulated by alkaline and by hyperosmolar preincubation and is most likely mediated by coexistent of apical H+-ATPase and H+,K+-ATPase. The main mechanism of net OH- secretion appears to be Cl-/HCO3- exchange at the apical side.