Glutathione metabolic responses to loaded breathing: variation
among respiratory muscles.
Supinski, G., D. Nethery, N. Murhez, R. Ciufo, A. Dimarco.
Pulmonary Division, Department of Medicine, Case Western Reserve
University and Metrohealth Medical Center, Cleveland, Ohio
APStracts 3:0248A, 1996.
Several studies have shown that loaded breathing elicits an oxidation
of GSH (reduced glutathione) to GSSG (oxidized glutathione) within
the diaphragm, but the effects of loaded breathing on GSH and GSSG
levels in other respiratory muscles have not been examined. The
present experiment examined this issue using decerebrate
unanesthetized rats in which a large inspiratory resistive load was
applied until respiratory arrest. Subsequently, muscle samples of
triangularis sterni, diaphragm (DIA), parasternal intercostal (PI),
upper rib cage lateral intercostal (UI), lower rib cage lateral
intercostal (LI), and soleus (SOL) were assayed for GSH and GSSG.
Glutathione levels were also measured on samples from unloaded
control animals. We found that DIA from loaded animals had lower GSH
than controls (i.e. GSH was 653 + 99 and 928 + 40 nmol/gm,
respectively for the DIA of load and control groups, p<.05),
higher GSSG (68 + 14 and 32 + 7 nmol/gm for load and controls,
p<.05) and higher GSSG/GSH ratios (17.0 + 6.0 and 3.7 + 0.9% for
load and controls, p<.05). Of the other muscles examined, only
the PI had comparable alterations in glutathione levels in response
to loading. Specifically, for PI muscles of load and control groups,
GSH was 427 + 75 and 618 + 40 nmol/gm (p<.05), GSSG was 71 + 16
and 20 + 5 nmol/gm (p<.01), and GSSG/GSH was 22 + 8 and 3.6 +
1.2% (p<.05). No other muscle demonstrated a significant
increase in GSSG or GSSG/GSH with loading, and only the LI had a
significant reduction in GSH. These findings indicate variation in
the degree of glutathione oxidation elicited by inspiratory loading
between the different respiratory muscles. The fact that
quantitatively similar glutathione alterations were observed in DIA
and PI suggests that these muscle groups may share a similar
propensity to generate free radicals during inspiratory loading.
Received 13 January 1995; accepted in final form 2 May 1996.
APS Manuscript Number A51-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96