The expression of ion channel mRNAs in skeletal muscles from patients with myotonic muscular dystrophy.

We investigated gene expression patterns of ion channels including the apamin-sensitive small-conductance Ca(2+)-activated K(+) (SK3) channel, the adult isoform of the skeletal muscle Na(+) channel (SkM1), the fetal isoform of skeletal muscle Na(+) channel (H1), and the Cl(-) channel (ClC-1) by using the semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) for muscle samples from patients with adult onset myotonic dystrophy (DM), amyotrophic lateral sclerosis, and polymyositis. Patients with DM showed a significant increase in SK3 mRNA but not in mRNAs for other ion channels. The increased expression of SK3 gene in DM did not correlate with H1, the marker of muscle denervation, or the percentage of type 2C fiber, the marker of muscle regeneration.