Temperature-induced functional deocclusion of thiols inhibitory for
sheep erythrocyte k-cl cotransport.
Lauf, Peter K., and Norma C. Adragna.
Departments of Physiology and Biophysics, and Pharmacology &
Toxicology, Wright State University, Dayton OH, 435401-0927 U.S.A
APStracts 2:0182C, 1995.
In low K sheep erythrocytes K-Cl cotransport is activated by treatment
with low concentrations of thiol reagents, and by other interventions
such as lowering of cellular free Mgi, hyposmotic cell swelling, the
kinase inhibitor staurosporine, and hydroxylamine. High
concentrations of N-ethylmaleimide (NEM) or methylmethane
thiolsulfonate (MMTS) reverse the activation through thiol groups
and, as shown here, also the stimulation by non-thiol manipulations.
The overriding inhibitory sites functionally associated with and
different from those of the activating thiols (SHa) were further
distinguished by temperature. Treatment with NEM and its subsequent
removal by dithiothreitol, both at OoC, prevented the inhibitory
effect at 37oC and thus the chemical modification of SHi. Whereas
stimulation through SHa closely followed the loss of glutathione
(GSH), inhibition through SHi only occured in GSH-depleted cells. The
reversal of K-Cl cotransport stimulation by all hitherto known
interventions, strongest in metabolically-depleted cells, suggests
that the low temperature-protected SHi constitute crucial sites
which, close to the transporter itself or at the cytoskeletal level,
become functionally deoccluded upon temperature elevation.
Received 6 December 1994; accepted in final form 26 April 1995.
APS Manuscript Number C709-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 9 May 1995.