Modification of aortic oxidative enzymes in rats by gonadectomy and substitutive therapy.

• In a recent paper, it has been shown that the gonads regulate the respiration of the aorta in rats, since aortic QO2 was increased by gonadectomy while it was restored to normal values through the injection of estradiol or testosterone. It was also reported that this metabolic depression was probably mediated through a direct hormonal mechanism in the arterial wall, because similar results could be reproduced in vitro. Related reports in the literature show that changes in respiration are not restricted to arteries, since gonadectomy also modifies the oxygen uptake in other organs. In the brain, for instance, the QO2 is raised by this procedure, while it is depressed in sexual structures. The gonadal hormones themselves also show a variable effect on the QO^ of different tissues. Testosterone depresses the QOL. of liver, kidney, and brain in rats, while estrogens show a similar effect only on liver and kidney; opposite conclusions have been reported by oilier authors.