Isolated perfused salamander proximal tubule. II. Monovalent ion replacement and rheogenic transport

Abstract

Early proximal tubules of the salamander kidney (A. tigrinum) were isolated and perfused in vitro. Transepithelial and basolateral electrical potential differences, transepithelial resistances and intracellular ionic activities were measured during removal of Na+, K+ or Cl- from the lumen, the bath or both lumen and bath. The effects of these external ionic replacements are interpreted in terms of an equivalent circuit that represents the renal epithelium as a network of passive ionic resistances, ionic diffusion potentials and active transport current sources. Apparently, rheogenic transport across the basolateral membrane is substantially diminished by removal of Na+ from either lumen or bath or by removal of K+ from the bath. Bilateral Cl removal produces an increase in transepithelial resistance but almost no change in the calculated rate of basolateral rheogenic ion flux may be a Na-K-ATPase that actively transports an excess of outward Na+ over inward K+.