Sensitivity of cardiac na+/k+ pump current to oxidant stress: role
of protein-sulfhydryl and non-protein sulfhydryl redox status.
Haddock, Peter S., Michael J. Shattock, and David J. Hearse.
Cardiovascular Research, The Rayne Institute, St. Thomas' Hospital,
London SE1 7EH, U.K.
APStracts 2:0075H, 1995.
Oxidant stress alters protein structure and function, possibly through
the modification of the redox status of regulatory protein sulfhydryl
groups. We used the sulfhydryl-blocking reagent p
-chloromercuriphenylsulfonic acid (pCMPSA), applied selectively and
independently to either the intracellular or extracellular
environment, to study the relationship between blocking protein
sulfhydryl groups and Na+/K+ pump current (ip). In voltage-clamped
(at -30 mV) guinea-pig ventricular myocytes, extracellular pCMPSA
(50, 100 and 400 [mu]mol/l) caused a concentration-dependent
reduction in holding current. Similarly, the selective intracellular
administration of pCMPSA (100 mmol/l) induced a similar inhibition of
ip, albeit over a longer time course. The inhibition of ip resulting
from either the intracellular or extracellular application of pCMPSA
(100 mmol/l) was reversed, in part, by the extracellular application
of dithiothreitol (3 mmol/l). An intracellular oxidant stress was
also imposed by using diethylmaleate to deplete the intracellular
non-protein sulfhydryl content (represented by reduced glutathione
(GSH)). In myocytes isolated from diethylmaleate-treated guinea-pigs
(860 mg/kg, intraperitoneally, 30 min before study), intracellular
GSH was depleted by 93 %, and ip was depressed by 38 % at all
membrane potentials tested. We propose that Na+/K+ pump function may
be related to protein and non-protein sulfhydryl status. Protein
sulfhydryl oxidation and glutathione depletion may account, in part,
for a depression in Na+/K+ pump activity during reperfusion-induced
oxidant stress.
Received 22 August 1994; accepted in final form 13 February 1995.
APS Manuscript Number H756-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.