Changes in nitric oxide and inducible nitric oxide synthase following stretch-induced injury to the tibialis anterior muscle of rabbit

This study investigated the changes in nitric oxide (NO) together with inducible nitric oxide synthase (iNOS) content and enzyme activity at 0, 4, 12, 24, and 48 h following acute muscle stretch injury. A single stretch injury was induced to the tibialis anterior muscle of 30 male New Zealand white rabbits (n = 6 at each time point). Injured and uninjured contralateral sham-operated muscles were harvested and analyzed for NO levels, iNOS content, and iNOS activity at each time point. Furthermore, three animals were used to estimate baseline NO levels and iNOS activity. There was a progressive reduction in NO content in the injured and the sham-operated muscles up to 24 h postoperation and stretch injury (p < 0.05). At 48 h postinjury, however, NO levels were 146% higher in injured muscles than in sham-operated muscles (p < 0.05). iNOS protein content was higher at 4 h and 48 h in injured versus shamoperated muscles (p < 0.05). Similarly, iNOS activity was higher at 4 h (p < 0.05) and at 48 h (p < 0.01) in injured versus sham-operated muscles. These results suggest that NO may play an active role during the postinjury recovery of skeletal muscle modulated by iNOS expression.