AJP - Lung Cellular and Molecular Physiology, Vol 267, Issue 3 350-L355, Copyright © 1994 by American Physiological Society
Effect of chronic respiratory loading on the subunit composition of cytochrome c oxidase in the diaphragm
Y. Akiyama, R. E. Garcia, L. J. Prochaska and A. R. Bazzy
Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06510.
To elucidate in the diaphragm, 1) whether chronic inspiratory loading
increases the amount of cytochrome c oxidase (COX) subunit proteins, and 2)
how well the regulation of mitochondrially and nuclearly coded COX subunits
is coordinated, we have trained six adult sheep with inspiratory
flow-resistive loads for 3 h/day for 3 wk. Six other sheep served as
controls. Proteins from crude muscle homogenates were separated using
sodium dodecyl sulfate polyacrylamide gel electrophoresis, immunoblotted,
and reacted with polyclonal rabbit anti-bovine COX antibodies. A
mitochondrially coded subunit (II) and nuclearly coded subunits (IV and
VII) reacted with anti-COX antibodies and were quantified with laser
densitometry using purified COX as a standard. In the costal diaphragm and
for the equivalent amount of muscle homogenate protein, the integrated
optical densities (IOD) for subunits II, IV, and VII were significantly
greater in the trained sheep than in the controls. Similarly, the IOD for
subunits II and VII were significantly greater in the trained than in the
controls in the crural diaphragm. There were no differences between the two
groups in the quadriceps, a muscle that was used as an untrained, internal
control muscle. The ratios of the IOD for each of the two nuclearly coded
subunits to that for mitochondrially coded subunit II were not different
between the two groups. These data suggest that chronic inspiratory loading
increases both mitochondrially and nuclearly coded COX subunits in the
diaphragm and that the subunits coded by the two genetic systems are
coordinately regulated.
