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Sex Differences in Cardiac Tolerance to Oxygen Deprivation - 40 Years of Cardiovascular Research

Experimental and clinical studies have clearly demonstrated significant sex differences in myocardial structure and function, both under physiological and pathological conditions. The best example are significant sex differences in the cardiac tolerance to ischemia/reperfusion injury: pre-menopausal adult female hearts are more resistant as compared to the male myocardium. The importance of these findings is supported by the fact that the number of studies dealing with this issue increased significantly in recent years. Detailed molecular and cellular mechanisms responsible for sex differences are yet to be elucidated; however, it has been stressed that the differences cannot be explained only by the effect of estrogens. In recent years, a promising new hypothesis has been developed, suggesting that mitochondria may play a significant role in the sex differences in cardiac tolerance to oxygen deprivation. However, one is clear already today: sex differences are so important that they should be taken into consideration in the clinical practice for the selection of the optimal diagnostic and therapeutic strategy in the treatment of ischemic heart disease. The present review attempts to summarize the progress in cardiovascular research on sex-related differences in cardiac tolerance to oxygen deprivation during the last 40 years, i.e. from the first experimental observation. Particular attention was paid to the sex-related differences of the normal heart, sex-dependent tolerance to ischemia-reperfusion injury, the role of hormones and, finally, to the possible role of cardiac mitochondria in the mechanism of sex-dependent differences in cardiac tolerance to ischemia/reperfusion injury. Key words: Female heart, Cardiac hypoxic tolerance, Ischemia-reperfusion injury, Sex differences.

Effects of chronic inhibition of Testosterone metabolism on cardiac remodeling after ischemia/reperfusion-induced myocardial damage in gonadectomized rats

The effects of testosterone on cardiovascular homeostasis are still not well understood. The objective of this work was to evaluate the effects of testosterone in the absence or presence of inhibition of Aromatase (4-hydroxyandrostenedione) and/or 5α reductase (Finasteride) enzymatic activities on the myocardial remodeling 30 days after ischemia/reperfusion (I/R) injury in gonadectomized rats. Results showed that testosterone administration to ORX rats resulted in decreased myocardial damaged area, inflammatory infiltrates and reduced MMP-3 and 13 expressions. Interestingly, Finasteride administration resulted in a greater decrease in scar tissue, inflammatory infiltrates, along with a significant decrease in MMP-3 and 13 expressions. In contrast, 4-hydroxyandrostenedione administrations increased all parameters. Our results suggest that testosterone does not have a direct effect since simultaneous inhibition of aromatase and 5α-reductase did not induce significant changes in I/R induced myocardial injury.

Summary: Coronary ischemia/reperfusion-induced injury in gonadectomyzed male rats is decreased by testosterone, protection is increased by blocking its 5α-reduction and blocked by inhibition of its aromatization.