Skeletal muscle cells express different isoforms of the calcium channel alpha2/delta subunit.

We examined developmental changes in calcium channel alpha2/delta subunit mRNA in skeletal muscle and their possible influence on L-type calcium currents (ICa-L). Several isoforms of alpha2/delta-1 mRNA were found in myotubes and muscle fibers, and their relative levels changed with time in culture or age of the animal. Levels of alpha2/delta-1a were largest in older myotubes and was the only alpha2/delta-1 isoform present in adult muscle. Both myotubes and muscle fibers also expressed low levels of alpha2/delta-2 and alpha2/delta-3 mRNA at all ages. alpha2/delta-4 mRNA could not be detected in either myotubes or muscle fibers. Changes in amplitude and voltage-dependent inactivation of the ICa-L concurred with the shift in alpha2/delta-1 isoform message, suggesting that alternative splicing of this subunit might be important for modulation of ICa-L.