AJP - Cell Physiology, Vol 256, Issue 4 C840-C848, Copyright © 1989 by American Physiological Society
Spectrophotometry of b-type cytochromes in rat brain in vivo and in vitro
C. A. Piantadosi
Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.
Terminal oxidase inhibitors such as cyanide (CN) and carbon monoxide (CO)
produce different absorption changes in the intact brain, suggesting
different mitochondrial responses to the inhibitors. In the present study,
the nature of the cytochromes involved in CO and CN responses in vivo was
investigated by low-temperature spectroscopy of rat brain, frozen in situ,
and of preparations of brain homogenate and isolated mitochondria.
Comparison of the spectra from different preparations at the high
resolution afforded by low-temperature spectroscopy indicated that
absorption responses to CO in vivo originated from mitochondrial b
cytochromes. Further detailed spectral analysis of mitochondrial
preparations revealed three CN-insensitive b cytochromes in nonsynaptic
brain mitochondria; one cytochrome could be reduced by succinate in the
presence of CN, the second could be reduced by succinate plus ATP, and the
third could be reduced only by anaerobiosis. The spectral characteristics
of the mitochondrial b cytochromes, when compared with spectra from
CO-exposed brain tissue frozen in situ, strongly implicated the
energy-dependent cytochrome b in the oxidation-reduction (redox) responses
caused by CO in vivo.
