Effects of pH on membrane resistance in normal and dystrophic mouse skeletal muscle fibers.

Membrane cable properties of skeletal muscle fibers of dystrophic mice (Rej-129) and their littermate controls were examined using a conventional two-microelectrode recording technique. Fibers from dystrophic mice had a decreased membrane resistivity (Rm) compared with those from normal mice (517 +/- 27 vs 642 +/- 34 omega - cm2), while the internal resistivities (Ri) did not differ significantly. The increase in membrane specific conductance was due to an increased Cl- conductance (gCl) (2304 vs 1346 microseconds/cm2 for normal fibers), although the K+ conductance (gK) was actually decreased (234 vs 369 microseconds/cm2 for normal fibers). With changes in pH, membrane conductances of normal and dystrophic skeletal muscle fibers varied differently, mainly due to differences in effects on the Cl- conductance. This contrast may be due to altered regulation of internal pH in dystrophic muscle.