Expression of Ca2(+)-ATPase isoforms in denervated, regenerating, and dystrophic chicken skeletal muscle

The expression of fast and slow isoforms of the sarcoplasmic reticulum Ca2(+)-ATPase was studied in denervated, regenerating, and dystrophic fast and slow avian skeletal muscles. We found that both fast and slow Ca2(+)-ATPase isoforms were expressed in most myofibers following denervation of adult fast-twitch muscle, but only the slow Ca2(+)-ATPase isoform was found in slow-tonic muscle which had been denervated. Regenerating myotubes in normally innervated and previously denervated adult fast-twitch or slow-tonic muscle expressed both Ca2(+)-ATPase isoforms. Expression of the slow Ca2(+)-ATPase isoform was found to persist in dystrophic fast-twitch muscle, long after it had disappeared from normal fast-twitch muscle. However, the fast Ca2(+)-ATPase isoform disappeared from slow-tonic muscle similarly in normal and dystrophic birds. These results demonstrate that the appearance of myosin heavy chain isoforms characteristic of developing muscle is correlated with similar changes in the expression of sarcoplasmic reticulum Ca2(+)-ATPases.