1986 年 50 巻 9 号 p. 829-838
We investigated the morphologic changes in the sarcoplasmic reticulum (SR) in acute myocardial ischemia, induced by occlusion of the coronary artery in the canine heart, by freeze-fracture of SR in situ and in vitro, and they were compared to the alterations in Ca++-stimulated ATPase activity and protein composition of the isolated SR. Both SR in situ and the isolated SR exhibited typical intramembranous particles with diameters of 70 to 90 Å in freeze-fracture replicas. The intramembranous particle density of the P face in SR in situ was 3, 319 ± 75 (mean ± SE) per μm2 and that in the isolated SR was 2, 667 ± 60 ; particles were more numerous on the concave (P) face than on the convex (E) face. In ischemia for 30 to 60 min a significant decrease in the number of particles was found in SR in situ, and the corresponding change was noted in the isolated SR. Simultaneous decreases in Ca++-stimulated ATPase activity and the major ATPase protein of the SR were recognized. The close correlation of the changing pattern between the reduction in Ca++-ports the suggestion that a large part of the intramembranous particles represent ATPase protein itself. Decrease in the SR membrane particles strongly suggests the degradation of ATPase protein in the process of ischemic myocardial injury.
