| 8023940 |
Del Castillo JR, Sulbaran-Carrasco MC, Burguillos L: K+ transport in isolated guinea pig colonocytes: evidence for Na (+)-independent ouabain-sensitive K+ pump. Am J Physiol. 1994 Jun;266(6 Pt 1):G1083-9.
K+ transport mechanisms in epithelial cells isolated from guinea pig distal colon have been studied using 86Rb as a tracer. A transport pathway has been identified that is proposed to be identical to the mechanism mediating transepithelial K+ absorption. Guinea pig colonocytes take up K+ through at least three separate mechanisms: 1) a Na (+)-dependent, ouabain-sensitive influx that is consistent with the Na (+)-K+ pump, 2) a Na (+)-dependent bumetanide-sensitive influx consistent with the Na (+)-K (+)-2Cl- cotransporter, and 3) a Na (+)-independent ouabain-sensitive influx, consistent with an apical colonic K+ pump. These transport mechanisms are sensitive to metabolic inhibition by rotenone and to vanadate, a blocker of type P adenosinetriphosphatase (ATPases). SCH-28080, an inhibitor of gastric K (+)-H (+)-ATPase, was without effect. Measurements of net K+ fluxes revealed that isolated colonocytes concentrated K+ by two processes: 1) a Na (+)-dependent ouabain-sensitive mechanism, which is compatible with the Na (+)-K+ pump and 2) a Na (+)-independent ouabain-sensitive mechanism consistent with the proposed absorptive K+ pump. These concentrative mechanisms were also inhibited by rotenone and vanadate, but not by SCH-28080. The Na (+)-independent ouabain-sensitive K+ pump was present in the distal colon, but absent in the proximal colon and the small intestine of guinea pig. It is proposed that this Na (+)-independent ouabain-sensitive K+ pump mediates K+ absorption and is related to the luminal K (+)-ATPase. |
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