The origin of muscle stem cells in rat triceps surae regenerating after mincing.

Rat triceps surae was minced and orthotopically autografted. Twitch time to peak, maxima tetanic tension, lactate dehydrogenase activity and total creatine concentration were measured in muscles regenerating for 30, 60 and 90 days. If the minces were frozen and thawed before grafting, muscle regeneration was suppressed. If they were further heated before grafting, muscle regeneration was also suppressed. If one half of the mince was either frozen and thawed or frozen, thawed and heated, and then recombined with the remaining half, muscle regeneration was delayed. However, at 90 days, 'intensive properties' (twitch time to peak, maximum tetanic tension, total creatine concentration and lactate dehydrogenase activity) of regenerates obtained from such partially treated minces were similar to those of regenerates obtained from untreated minces although their 'extensive properties' (weight and maximal tetanic force) were approximately halved. The extent of regeneration depends on the mass of untreated mince autografted and thus, presumably, on the number of viable muscle stem cells initially present in the mince.