ACETYLCHOLINE-RECEPTOR AND CALCIUM LEAKAGE ACTIVITY IN NONDYSTROPHIC AND DYSTROPHIC MYOTUBES (MDX)

To determine whether the lack of dystrophin alters the occurrence of c alcium leakage activity (CLA) and acetylcholine receptor (AChR) activi ty, the frequency of each event class was determined from several cell attached patches on nondystrophic and dystrophic (mdx) myotubes, The frequency of CLA observed in the presence of ACh was significantly (P < 0.05) elevated in mdx myotubes, an effect which was partly due to a significant (P < 0.05) increase in the proportion of cell attached pat ches that exhibited 100% CLA with no AChR activity. Areas of mdx and n ondystrophic membrane that exhibited reduced or absent AChR activity h ad significantly (P < 0.01) and substantially elevated calcium leakage event frequencies. This inverse and discontinuous relationship betwee n CLA and AChR activity provides further evidence that some CLA in dys trophic muscle is produced by clusters of AChRs that form unusual phys ical associations with the dystrophic cytoskeleton during the processe s associated with receptor localization and stabilization. (C) 1996 Jo hn Wiley & Sons, Inc.