Increase of cardiac work is associated with decrease of
mitochondrial nadh.
Ashruf, J. F., J. M. C. C. Coremans, H. A. Bruining, C. Ince.
Dept. of General Surgery, Erasmus University of Rotterdam, The
Netherlands, Dept. of Anaesthesiology, University of Amsterdam, The
Netherlands
APStracts 2:0122H, 1995.
In this study we investigated the effect of work and substrate supply
on the mitochondrial NADH/NAD+ ratio using epicardial
autofluorescence in rat hearts perfused according to Langendorff. To
avoid vasoconstrictory effects during high work output, nitroprusside
containing Tyrode was used. Photo-bleaching was avoided by using
discontinuous UV excitation for NADH fluorescence measurements. To
increase work, heartbeat rate was raised from 5 to 7 Hz and
concomitantly left ventricular pressure was raised step-wise from 0
to +/- 90 mm Hg. During substrate limited (5.5 mM glucose)
perfusions, increase in oxygen consumption (3.5 +/- 0.4
[mu]mol/min/g, mean +/- SE, n=6) caused by increase of heartbeat
rate, was associated with significant decrease of NADH fluorescence
(-31 +/- 2.5 %, mean +/- SE, n=6). During perfusions with 10 mM
pyruvate increase of oxygen consumption (3.6 +/- 0.7 [mu]mol/min/g,
mean +/- SE, n=6) was associated with significant decrease of NADH
fluorescence (-20 +/- 2.6 %, mean +/- SE, n=6). These results suggest
that a rise in the mitochondrial NADH/NAD+ ratio is not the primary
stimulus for increase in respiration and that changes of the
mitochondrial NADH/NAD+ ratio are secondary to changes in oxygen
consumption.
Received 2 November 1994; accepted in final form 22 March 1995.
APS Manuscript Number H972-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 4 April 1995.