Effects of Anoxia on Metabolism of Myocardial Tissue

Abstract

Anoxia in vivo produced alterations in respiratory processes of myocardial tissue as indicated by decreased O2 consumption of tissue homogenates. The O2 uptake of homogenized myocardial tissues from rats subjected to anoxia was only 50% that of homogenates from normal animals. Manometric estimation of lactic acid dehydrogenase showed no difference in the activity of this enzyme in myocardial tissues of normal rats and those exposed to low O2 tensions. A moderate reduction in coenzyme I and cytochrome c was observed in the hearts of rats subjected to anoxia. The observed reductions, 17% in coenzyme 1 and 30% in cytochrome c, were slight but significant. The O2 consumption of homogenized myocardial tissue from anoxic rats could be restored to normal by supplementation with an aqueous extract of boiled hearts from normal rats. Thus, the reduced 02 consumption of myocardial tissue homogenates from animals subjected to O2 deficiency resulted from loss or inactivation of heat-stable rather than heat-labile substance. The decreased O2 consumption of anoxic myocardial tissue was not caused by destruction of the respiratory enzymes themselves but rather by a deficit of factors essential for normal enzyme activity.