Contractile and histochemical properties of sliced muscle grafts regenerating in normal and denervated rat limbs.

Rat extensor digitorum longus muscles were transversely sliced into 7-8 segments. The muscle slices were autografted back into their original beds. In one series the recipient limbs were normal and in the other, limbs were denervated. At postoperative intervals of 7, 14, 30, and 60 days, the contractile properties (latency period, contraction and half relaxation times, time parameters of contraction of twitch and tetanus, and twitch and tetanic tension) and histochemical properties (succinic dehydrogenase and myofibrillar ATPase) were analyzed. Sliced grafts regenerating in normally innervated legs followed a typical conversion from slow to fast contraction times, whereas regenerates in denervated limbs remained slow. Histochemically, innervated regenerates developed a heterogeneous pattern of muscle fiber type staining during the second month, whereas different histochemical types of muscle fibers did not appear in noninnervated regenerates. As in ontogeny, denervation retards or prevents the full structural and functional differentiation of regenerating muscle fibers.