Effects of temperature, medium K +, ouabain and ethacrynic acid on transport of electrolytes and water by separated renal tubules

Abstract

1. 1. Isolated tubules from rabbit renal cortex are loaded with Na +, Cl −, water and leached of their K + by incubation at 0.5°C in a K −-free medium. Three aliquot fractions of the preparation are incubated: at 0.5 °C in a K +-free medium, at 28 °C in a K +-free medium, at 28°C with 5 mM,[K +] 0, respectively. The incubation at 0.5 °C is used as a control. The tubules incubated at 28 °C, K +-free, lose an isotonic NaCl solution and maintain nearly their whole K +. Those incubated at 28 °C with 5 mM [K +] 0, gain K + and lose water, Na + and Cl − in such a way that the increase of the K + intracellular concentration is exactly balanced by the decrease of the Na + plus Cl − intracellular concentrations. 2. 2. Both extrusion of Na + (with Cl and water) from leached tubules, incubated at 28°C in a K +-free medium, and exchange of Na + for K + in leached tubules rewarmed with 5 mM [K +] 0, are completely inhibited by ouabain and ethacrynic acid, which simultaneously induce an important K + tissular depletion. 3. 3. When leached tubules are incubated at 0.5 °C or 28 °C in K + free medium, small amounts of this ion appear in the incubation medium. Tubular leakage is likely to account for these traces of K +. Incubation of leached trubules in a K +-free medium (except for tracer 42KCl) induces a rapid exchange of tissular K + for medium K + at 28 °C, and a much smaller one at 0.5 °C. 4. 4. When recapture of the escaped K + is partially prevented by dialysis of tubules suspension against a K +-free medium, the K + tissular content is significantly reduced as well as the extrusion of Na +, Cl − and water. 5. 5. It is concluded that both the net efflux of Na − (with Cl − and water) induced by the rewarming of leached tubules into nominally K +-free solutions, as well as the Na +−K + exchange, demand the simultaneous movement of K + into the cells. It is further concluded that ions and water transport by renal tubular cells is governed in some manner by cell electrolyte composition.