Anastomoses of transverse tubules with terminal cisternae in polymyositis.
Abnormal transverse or T tubules spatially continuous with sarcoplasmic reticulum (SR), as visualized with a lanthanum (La) tracer, were found in biopsy specimens from nine patients with polymyositis whose serum enzyme (creatine phosphokinase [CPK]) levels were elevated before the time of biopsy. On comparison with the T system in more than 50 control subjects without CPK elevation, it became apparent that presumed anastomoses of T tubules with SR were the most consistent anatomical correlates of the enzyme leakage. Two types of anastomoses were seen on the basis of passage of La: first, early segmental dilation of T tubules and perpendicular continuations with SR; and second, focal proliferation of T tubules forming "T tubule networks" and then anastomosing with SR at the periphery of the networks. The latter is considered to be a concurrent repair process for the injured triads. Lanthanum did not penetrate freely through the plasma membrane of necrotized muscle fibers. It is concluded that junctional sites between T tubules and SR may be the primary sites of leakage of sarcoplasmic enzymes in polymyositis.
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003402:Creatine Kinase / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D009132:Muscles / Q000201:enzymology / Q000648:ultrastructure*; D009220:Myositis / Q000201:enzymology / Q000209:etiology / Q000473:pathology*; D012519:Sarcoplasmic Reticulum / Q000648:ultrastructure
D003402:Creatine Kinase