Defining the volume dependence of multiple k flux pathways of trout red cells. Berenbrink, Michael, Yasmin R. Weaver, and Andrew R. Cossins. Integrative Physiology Research Group, School of Biological Science, University of Liverpool, Derby Building, LIVERPOOL L69 3BX, U.K. and *Institut fuer Tierphysiologie, Humboldt-Universitaet zu Berlin, Philippstrasse 13, Abderhaldenhaus, D-10115 BERLIN, Germany.
APStracts 3:0390C, 1996.
The volume-sensitivity of different K flux pathways has been determined in trout red cells subjected to volume perturbation. Gentle hyposmotic swelling induced a K influx in a Cl-containing saline but not in a NO3 or methane sulfonate (MeSF) containing salines, consistent with the activation of a Cl-dependent flux. Extreme hyposmotic swelling led to larger K fluxes in all salines but with reduced anion discrimination of the Cl-dependent flux.. In contrast to these graded responses, isosmotic swelling using ammonium chloride or [beta]-adrenergic stimulation activated only Cl-dependent fluxes in an all-or-none fashion. The relationship between the hyposmotically- and isosmotically-induced pathways was studied by co -activation using either ammonium chloride or isoproterenol with anisosmotic treatment. Cells in ammonium chloride-containing hyposmotic salines showed no additive K flux over that induced by hyposmotic treatment alone, indicating that the isosmotically -induced, Cl-dependent flux was identical to the hyposmotically -induced, Cl-dependent flux. However, cells coactivated by hyposmotic and [beta]-adrenergic treatment showed a small Cl-dependent flux in addition to that induced by hyposmotic treatment alone. This small third component was unaffected by anisosmotic treatment. We conclude that the major Cl-dependent and Cl-independent K flux pathways are distinct and separate and that the former has a anion-dependence that varies with cell volume and a volume sensitivity that varies with ionic strength. 

Received 13 May 1996; accepted in final form 1 November 1996.
APS Manuscript Number C260-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996