AJP - Heart and Circulatory Physiology, Vol 245, Issue 6 998-1006, Copyright © 1983 by American Physiological Society
Effect of hypoxia and reoxygenation on mitochondrial function in neonatal myocardium
H. H. Young, T. Shimizu, K. Nishioka, T. Nakanishi and J. M. Jarmakani
The effect of hypoxia and reoxygenation on mitochondrial function was
studied in the newborn and adult rabbit hearts. In control muscle,
mitochondrial state 3 respiration (state 3 QO2), respiratory control index
(RCI), energy-dependent calcium uptake, ATP content, and adenine nucleotide
translocase in the newborn were significantly greater than in the adult.
After 60 min hypoxia, both the newborn and adult showed significant
decrease in 1) tissue glycogen, adenine nucleotides, and creatine
phosphates and 2) mitochondrial adenine nucleotides, adenine nucleotide
translocase, and glutamate-supported state 3 respiration. In the adult,
reoxygenation following 60 min hypoxia was not associated with significant
recovery in any of the variables described above, and there was significant
decrease in the rate of calcium uptake. In the newborn, the values of all
variables returned to control except for tissue glycogen and adenine
nucleotide translocase. The data suggest that the effect of hypoxia on
mitochondrial function in the newborn is less than in the adult. This
occurs because of 1) the lower energy demand in the newborn, 2) higher
tissue glycogen and higher rates of glycolysis in the newborn, 3) increased
degradation and/or efflux of ATP and ADP in the adult, and 4) possibly a
difference in the sarcolemmal resistance to hypoxia in the two age groups.
