ISCHAEMIA: Reperfusion damage causes injury both cardiomyocytes and endothelialcells. Loss of endothelium function and heart cells degeneration can be essential for deterioration ofpostoperative efficiency of heart and in this way can threaten patients' life. OBJECTIVE: How additionof L-arginine to cardioplegic solution influences development of ultrastructural degeneration indicationsof rat's heart exposed to cold cardiolegic ischemia. METHODS: The research was conducted on isolatedheart model of 56 rats, divided into seven equal groups. The hearts were prepared with modified Neely'smethod and were perfused with the use of apparatus in accordance with modified Langedorf's method. Theresearch was carried out in order: initial perfusion of the non-working and working heart, perfusionwith cardioplegic solution, cold cardioplegic arrest with or without addition of L-arginine. RESULTS:In the microscopic preparations of rat's heart in the control group (P) numerous focal performing contractionnodes were found. Intumescent vessels' endothelium included a large number of pinocytal vesicles. Inthe ultrastructural examination of group DI heart preparations there were less contraction nodes thanin control group. The widening of endoplasmatic reticulum's channels and system T was essentially smallercomparing with group P. Less widening of perivascular zone and less number and size of pinocytal vesicleswere also observed. In group 2 further decreasing of contraction nodes number was revealed. The structureof capillary was preserved and number of pinocytal vesicles was still decreasing. Further standardizationof ultrastructural picture of cardiomyocytes and perivascular zone was found in group 3. CONCLUSION:In control group (P) microscopic degeneration indications of rat's heart were the most intensified. Additionof L-arginine to cardioplegic solution influenced decreasing of intensification of heart degenerationindications. Increasing of L-arginine doses added to cardioplegic solution positive correlates with protectiveeffect of L-arginine on heart ultrastructure.

Keywords: Myocardium - ultrastructure