Changes in myosin heavy chain mRNA and protein isoforms of rat muscle during forced contractile activity

The absolute amounts of messenger RNA for four isoforms of the rat myosin heavy chain (MHC) were measured using a quantitative reverse transcriptase-polymerase chain reaction to determine the effect of chronic low-frequency stimulation on the proportion of the MHC isoforms. Results reveal that the fast twitch muscle of the rat extensor digitorum longus has a limited capacity for fast-to-slow conversion.