SODIUM WITHDRAWAL CONTRACTURES IN DEVELOPING AND REGENERATING RAT EXTENSOR DIGITORUM LONGUS MUSCLES

During postnatal development of extensor digitorum longus (EDL) muscle , sodium withdrawal contractures were observed during the first 6 days after birth, and not after this time. In regenerating EDL muscles, ze ro-Na contractures were demonstrated: (1) 7 days after bupivacaine inj ection, but not 14 or 90 days after this injection; (2) 7, 14, and 90 days after autotransplantation; and (3) 7, 14, and 90 days after the i ntervention in sliced muscles. The present findings emphasize the role of the denervation in the development of zero-Na contractures in the regenerating muscles and suggest that a calcium-sodium exchange across the sarcolemma may appear in these muscles. (C) 1998 John Wiley & Son s, Inc.