ULTRASTRUCTURAL ALTERATIONS IN MITOCHONDRIAL-MEMBRANES OF ISCHEMIC MYOCARDIUM AS REVEALED BY FREEZE-FRACTURE TECHNIQUE

Mitochondrial membranes of ischemic myocardium were studied with freeze-fracture electron microscopy. Four fracture faces, two each from inner and outer membranes, were exposed. The protoplasmic leaflet or P face contained more intramembranous (IM) particles per μm2 than the exoplasmic or E face of the same membrane. Mitochondria became swollen after coronary artery occlusion. The density of IM particles was more reduced on the outer membrane than on the inner membrane of mitochondria examined from myocardium ischemic for 45 min. Aggregation of IM particles was prominent in the tissue reperfused after 45 min of ischemia. Upon progression of ischemia the density of IM particles on both outer and inner membranes was reduced approximately by 50% in mitochondria from myocardium rendered ischemic for 2 and 24 h. More areas of the lipid bilayer which lacked IM particles were exposed in mitochondria examined from myocardium ischemic for 24 h and showed several successive undelineated fracture planes. These findings suggest that myocardial ischemia induces alterations in the lipid fluidity and the distribution pattern of IM particles of the mitochondrial membranes. © 1978.