Electrophoretic analysis of the contractile proteins of the
diaphragm in chronically hypoxic rats.
Mortola, Jacopo P., and Lina Naso.
Department of Physiology, McGill University, Montreal, Quebec,
Canada
APStracts 2:0270C, 1995.
We questioned whether the relative composition of the diaphragm
proteins [myosin heavy chain (MHC), actin (A), tropomyosin (TM)
[alpha] and [beta], and MHC isoforms] was altered by chronic hypoxia.
Rats were exposed to hypobaric hypoxia (inspired O2 pressure _95 mm
Hg) from birth for 60 days or 9-11 months. From the muscle
homogenate, relative proteins content was computed by densitometric
analysis following protein separation with polyacrylamide gel
electrophoresis and identification by immunoblotting. The relative
concentrations of MHC, A, TM[alpha] and TM[beta] did not differ from
those of control rats for either duration of exposure. The main MHC
isoforms (I, IIa,IIb, IIx) remained unaltered after 60 days, but
changed significantly after 9 months of hypoxia, mostly because of a
decrease in the slow (I) component and an increase of II complex. We
conclude that chronic hypoxia of long duration modifies the
expression of MHC isoforms in the rat diaphragm. Qualitative similar
changes also occurred in a muscle of the thigh, the rectus femoris;
hence, the changes in diaphragm MHC probably reflected the systemic
effects of hypoxia, rather than the increased mechanical load imposed
by the chronic hyperventilation.
Received 27 February 1995; accepted in final form 7 July 1995.
APS Manuscript Number C108-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.