Qualitative and quantitative changes in the ultrastructure of the dog heart after temporary ischaemia and coronary reperfusion.

A total ischaemia of one area of the myocardium was produced by ligature of a coronary artery in dogs. After 30 min, 1 hr, 2 hrs, and 4 hrs the ligature was loosened and the artery was for 1--2 hrs reperfused up to 4--7 days. At the end of the ischaemia and after reperfusion the ultrastructure of the myocardium was qualitatively and morphometrically investigated. The findings concerned: loss of glycogen (partly glycogen accumulation), mitochondrial swellings and fusions and development of megamitochondria, loss of cristae, rupture of the mitochondrial outer membranes, relaxation or supercontraction of the myofibrils, vesicular and vacuolar changes of the sarcoplasmic reticulum, oedema of the sarcoplasm, rupture of the sarcolemma. No significant differences of the quantitative parameters could be observed during the ischaemia from 30 min to 4 hrs: myofibrils 53.65--59.74%, mitochondria 26.51--33.59%, sarcoplasm 8.22--11.86%, sarcoplasmic reticulum 1.41--2.63%, lipofuscin 0.05--0.87%, lipids 0.01--0.10%. In comparing the data of the single animals we could determine significant differences between some parameters at the ends of the ischaemic phase and of the reperfusion phase, but as far as the findings are concerned both increases and decreases could be observed. The investigations show that the limit of the reversibility of damages in myocardial cells is about 45 min; in special cases a longer survival time may be taken into account. Reperfusion has different, though not always positive, effects.