Na+ pump in renal tubular cells is regulated by the endogenous Na+,K+-ATPase inhibitor from hypothalamus

11. CANTIELLO HF, CHEN E, RAY S, AND HAUPERT GT

AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY

Año: 1988 p. 574 - 580

0363-6143

Bovine hypothalamus contains a high affinity, specific, reversible inhibitor of mammalian Na’- K’-ATPase. Kinetic analysis using isolated membrane fractions showed binding and dissociation rates of the hypothalamic factor (HF) to be (like ouabain) relatively long (off rate = 60 min). To determine whether the kinetics of inhibition in intact cells might be more consistent with regulation of physiological processes in vivo, binding and dissociation reactions of HF in intact renal epithelial cells (LLC-PK1) were studied using “Rb+ uptake and [3H]ouabain binding. As with membranes, a 60-min incubation with HF inhibited Na’-K’- ATPase in LLC-PKI cells. In contrast to membrane studies, no prolonged incubation with LLC-PK1 was needed to observe inhibition of Na+-K’-ATPase. HF caused a 33% inhibition of ouabain-sensitive @Rb’ influx within 10 min. Incubation of cells with HF followed by washout showed rapid reversal of pump inhibition and a doubling of pump activity, The doseresponse curve for HF inhibition of LLC-PK1 86Rb+ uptake showed a sigmoidal shape consistent with an allosteric binding reaction. Thus HF is a potent regulator of Na”-K’-ATPase activity in intact renal cells, with binding and dissociation reactions consistent with relevant physiological processes. 10 min. Incubation of cells with HF followed by washout showed rapid reversal of pump inhibition and a doubling of pump activity, The doseresponse curve for HF inhibition of LLC-PK1 86Rb+ uptake showed a sigmoidal shape consistent with an allosteric binding reaction. Thus HF is a potent regulator of Na”-K’-ATPase activity in intact renal cells, with binding and dissociation reactions consistent with relevant physiological processes.