Ischemic postconditioning provides cardioprotective and antiapoptotic effects against ischemia-reperfusion injury through iNOS inhibition in hyperthyroid rats.

Ischemic postconditioning (IPost) is a strategy to provide protection against ischemia-reperfusion (IR) injury. The cardioprotective effects of IPost in cases of ischemic heart disease along with co-morbidities like hyperthyroidism remain unknown. The aim of this study was to investigate the effects of IPost on expression of eNOS, iNOS, Bax, and Bcl-2 genes in hyperthyroid male rats, subjected to myocardial IR. Hyperthyroidism was induced by adding thyroxine to drinking water for a period of 21 days. Using the Langendorff device hearts were perfused, then subjected to a 30-minute global ischemia which was followed by 120 min of reperfusion; subsequently IPost was induced immediately after ischemia. Results indicated that following IR, expression of eNOS and Bcl-2 decreased, whereas expression of iNOS and Bax increased in both the control and hyperthyroid groups. In hyperthyroid animals, IPost significantly increased expression of eNOS by 3.19 fold and Bcl-2 by 3.66 fold; it also decreased expression of Bax by 51%, and reduced IR-induced DNA laddering pattern and infarct size (45.7 ± 1.82% vs. 59.3 ± 1.83%, p<0.05) in the presence of aminoguanidine (AG), a selective iNOS inhibitor. In conclusion, IPost per se could not provide cardioprotection against myocardial ischemia in hyperthyroid rats, a loss of which however was restored by the combination of IPost and iNOS inhibition that acts by a decrease in Bax and an increase in both eNOS and Bcl-2 expression.