AJP - Heart and Circulatory Physiology, Vol 243, Issue 4 619-H627, Copyright © 1982 by American Physiological Society
NAD/NADH: redox state changes on cat brain cortex during stimulation and hypercapnia
L. Gyulai, E. Dora and A. G. Kovach
The redox state of the anterior suprasylvian gyrus of cats was measured
during electrical stimulation and under hypercapnia on cast immobilized and
artificially respirated. The state of the nicotinamide adenine
dinucleotide-reduced nicotinamide adenine dinucleotide (NAD/NADH) redox
system was monitored by in vivo fluorometry. Hypercapnia was produced by
inhalation of 10, 15, and 30% CO2, respectively. Hypercapnic acidosis led
to NADH oxidation. The NADH oxidation under 30% CO2 inhalation was
significantly larger (-14.9 +/- 2.9%) than that observed under 10% (-6.5
+/- 1.9%) and 15% CO2 (-7.0 +/- 1.6%) inhalation. Under normocapnic
conditions, stimulation induced NAD reduction to NADH (5.5 +/- 0.8%). The
magnitude of the NAD reductive response to stimulation was unaffected by
10% CO2 inhalation, but it was decreased by 15 and 30% CO2 inhalation. The
increased concentration of NADH upon stimulation is interpreted as
resulting from an increased rate of substrate mobilization. The cause of
the oxidation of the NADH pool of the cell during hypercapnia is partly due
to the direct inhibitory effect of CO2 on the carbohydrate metabolism, but
the role of other mechanisms cannot be neglected either.
