Medical Journal of The Islamic Republic of Iran (MJIRI)

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It has been known that cardiomyocytes possess a remarkable ability to downregulate their energy expenditure on restricted 02 supply. However it has also been speculated that an ability to suppress aerobic respiration and ATP utilization could be a protective response to prolonged hypoxia. Having the role of the cytochrome oxidase enzyme in mind, one can ask if its inhibition by using cyanide has a role in improving the heart's function after the cardioplegic period. In order to answer this question, the present study was carried out on two groups of rats. The test and control groups included 10 male rats. Each animal in both test and control groups received cyanide (LP., 1.6 mg/kg/ day) and saline (1 ml/day) respectively, and each heart experienced three stages: 1) normal activity, 2) cardioplegia, and 3) reperfusion stage. St-Thomas II cardioplegic solution was used while it contained 0.5 mmol/L cyanide in the test group. The results indicated that recovery percentage in the reperfusion stage, for the De.L. v.P. and dp/dt parameters were significantly higher in the test [(14S.1%±11.97) and (l30.97%±9.619)] than the control group [(91.62%±4.S9) and (96.1 %±4.91)] [(P<0.01) and (p<0.005)]. H.R. parameters, the rate of coronary solution flow, the variations of left ventricular diastolic pressure in the reperfusion period and tissue pathologic damages did not show significant differences between the two groups. These results indicated that the application of cyanide in cardioplegic solution induces an improvement of cardiac function in relation to the control group which is likely to be due to the impact of cyanide on cytochrome oxidase.

Keywords: Cardioplegia, Cyanide, Cytochrome oxidase.

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