AJP - Cell Physiology, Vol 255, Issue 1 C112-C122, Copyright © 1988 by American Physiological Society
Pathways of Cl- transport in human fibroblasts
P. Lin and E. Gruenstein
Department of Biochemistry and Molecular Biology, University of Cincinnati College of Medicine, Ohio 45267-0522.
Three pathways of Cl- efflux were identified in normal human fibroblasts.
Twenty percent of the total Cl- efflux is via an electrically conductive
pathway with an efflux constant of 0.016 min-1. This pathway is insensitive
to 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and bumetanide
but is partially inhibited by anthracene-9-carboxylic acid. Twenty-five
percent of the Cl- efflux occurs via Cl- with cation cotransport having an
efflux constant of 0.020 min-1. This pathway is inhibited by bumetanide and
is dependent on the simultaneous presence of Na+, K+, and Cl-. Under basal
conditions, the energetics of this pathway indicate that it is operating
close to equilibrium. Fifty percent of the Cl- efflux occurs via an anion
exchange pathway having an efflux constant of 0.040 min-1 that is inhibited
by DIDS or by removal of Cl- from the extracellular medium. Together these
pathways account for 95% of the total Cl- efflux.
