NITROGLYCERIN-INDUCED DIRECT PROTECTION OF THE ISCHEMIC MYOCARDIUM INISOLATED WORKING HEARTS OF RATS WITH VASCULAR TOLERANCE TO NITROGLYCERIN

We investigated whether nitroglycerin (NTG) was able to produce an ant i-ischaemic effect in isolated working hearts of rats with vascular to lerance to NTG. Hearts isolated from tolerant and non-tolerant rats we re subjected to 10 min coronary occlusion in the presence of 10(-7) M NTG and/or its solvent. NTG alleviated ischaemia-induced deterioration of cardiac function and decreased lactate dehydrogenase release whils t having no effect on coronary flow nor the area of the ischaemic zone both in hearts isolated from NTG-tolerant and non-tolerant rats. The magnitude of the effect was similar in the two groups. These results s uggest that the anti-ischaemic effect of NTG involves direct myocardia l mechanisms independent of its vascular action and that vascular tole rance to NTG does not affect this direct protective action.