Modification of Aortic Oxidative Enzymes in Rats by Gonadectomy and Substitutive Therapy

Abstract

Activity of the following enzyme systems has been determined in homogenates of aortas from rats: "succinic dehydrogenase," cytochrome oxidase, oxidation of α-ketoglutaric acid and of fumaric acid, DPN- and TPN-linked dehydrogenases, as well as lactic dehydrogenase. The following groups of animals were studied: (1) intact males; (2) castrated males; (3) castrated males injected with testosterone; (4) intact females; (5) spayed females; (6) spayed females injected with estradiol. Results demonstrated that gonadectomy in males stimulated "succinic dehydrogenase" and depressed the oxidation of fumaric acid; these effects were reversed by the injection of testosterone. Castration did not modify the activity of cytochrome oxidase, oxidation of α-ketoglutaric acid, DPN- and TPN-linked dehydrogenases, nor lactic dehydrogenase. Gonadectomy in females resulted in stimulation of "succinic dehydrogenase," cytochrome oxidase, as well as oxidation of α-ketoglutaric acid; these effects were reversed by the injection of estradiol into spayed females. No clear results were obtained in connection with oxidation of fumaric acid and no modifications were observed in the activity of DNP- and TPN-linked dehydrogenases nor in lactic dehydrogenase. Experiments performed in vitro showed that sexual hormones were able to depress the activity of oxidative systems in aortic homogenates.