Dysfunction of the sarcoplasmic reticulum in polymyositis.
The transport of calcium in vesicles of sarcoplasmic reticulum isolated from muscle specimens from 6 patients with early, active polymyositis and from 11 controls was examined. The time courses of calcium uptake and calcium-dependent ATPase activity were measured simultaneously. Calcium uptake by sarcoplasmic reticulum vesicles from patients with polymyositis was 50% less than that by vesicles from controls (P less than 0.001). In contrast, no difference in calcium-dependent ATPase activity was noted between vesicles from patients with polymyositis and controls. The demonstrated defect may be important in the pathogenesis of muscle weakness in polymyositis.
D000293:Adolescent; D000328:Adult; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D003882:Dermatomyositis / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009135:Muscular Diseases / Q000378:metabolism; D009220:Myositis / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D013997:Time Factors
D000252:Calcium-Transporting ATPases; D002118:Calcium