Poly (A)+ mRNA was isolated from rat satellite cell cultures and analyzed by Northern blot analyses for mRNA content of phosphoglycerate mutase (PGAM) isozymes. In non-differentiating satellite cells only PGAM-B mRNA was detected, but when cells were differentiated into myotubes, which undergo spontaneous contraction, mRNA for PGAM-M muscle-specific isozyme was also detected. This finding is in perfect concordance with the transition of PGAM isozymes encountered in the same cell cultures, and strongly supports a transcriptional control of PGAM expression throughout myogenesis independently of nerve influence.
