Analysis of muscle proteins in acute quadriplegic myopathy

We investigated the changes of muscle proteins in acute quadriplegic myopat hy (AQM) using immunohistochemistry and stoichiometry. Cases of AQM were ob served in which it was difficult to type muscle fibers with adenosine triph osphatase staining in biopsied muscle. Well-defined typing of these cases w as possible by performing immunofluorescent staining using slow and fast sk eletal troponin I (Tnl) antibodies. By this means, small angular fibers wer e shown to be fast skeletal muscle, and myosin was absent from these muscle fibers. Actin and tropomyosin were maintained. Muscle protein ratios were determined by stoichiometry following sodium dodecyl sulfate-polyacrylamide gel electrophoresis of AQM myofibril specimens from four subjects. The myo sin heavy chain/actin ratio was significantly decreased compared with a nor mal control group and other neuromuscular diseases. These pathologic findin gs returned to normal during recovery from AQM, Thus, myosin selectively de creases, whereas actin and regulatory proteins located above it are maintai ned during AQM. (C) 2000 John Wiley & Sons, Inc.