Key result
Surgical cardiac denervation in dogs increased in vitro myocardial oxygen consumption without significantly altering succinate dehydrogenase (19.4 vs 20.3 pmol.H2.cm-2.s-1) or cytochrome oxidase.
Why the study?
Does surgical cardiac denervation alter myocardial oxygen consumption in dogs?
Does surgical cardiac denervation alter myocardial oxygen consumption in dogs?
Chronically denervated dog hearts exhibit increased oxygen consumption that is not driven by changes in mitochondrial enzyme activities.
Denervation increases myocardial O2 consumption independently of mitochondrial enzymes in dogs; hypothesis-generating with uncertain human relevance.
Surgical cardiac denervation was carried out in dogs under halothane anaesthesia. In a paired experimental design control biopsy specimens were obtained before surgical denervation. The dogs were allowed to recover and three weeks to elapse before the second biopsy specimen was taken. Both right and left ventricular specimens had higher in vitro oxygen consumption after denervation than before. Other specimens were immediately cooled in hexane at -60 degrees C and stored under liquid nitrogen until analysed. Succinate dehydrogenase and cytochrome oxidase activities were then measured histochemically in sequential 10 or 12 microns sections. There was no significant difference between the enzyme activities measured before or after cardiac denervation (succinate dehydrogenase 20.3(6.3) before, 19.4(4.02) pmol.H2.cm-2.s-1, after; cytochrome oxidase 223(73.4) before, 263(61.6) (measured as extinction coefficient) after). Thus the changes in oxygen consumption in the chronically denervated dog heart are not due to any lack of these mitochondrial enzymes.
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Butcher et al. (1987) studied Surgical cardiac denervation. Surgical cardiac denervation vs. Before surgical denervation (paired control) was evaluated on Succinate dehydrogenase and cytochrome oxidase activities. Surgical cardiac denervation in dogs increased in vitro myocardial oxygen consumption without significantly altering succinate dehydrogenase (19.4 vs 20.3 pmol.H2.cm-2.s-1) or cytochrome oxidase.
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