Role of Nitric Oxide in the Apoptosis of Structural Damage in Rat Skeletal Muscle

Abstract

PURPOSE: Apoptosis is a common mechanism of programmed cell death that has been implicated in the development of skeletal muscle damage. We examined the role of nitric oxide (NO) in the apoptosis of skeletal muscle damage. METHODS: A standardized eccentric stretch injury was created to the tibialis anterior (TA) muscle of 40 male Wistar rats (200 to 240 g), using a customized isokinetic test device and electrical stimulation. We evaluated the effects of the nitric oxide synthase inhibitor N(G)-nitro-L-arginine-methyl ester (L-NAME; 85 mg/kg/day) on apoptosis in rat skeletal muscle cell. The TA muscle was isolated immediately, 1, 3 and 7 days after muscle stretch injury. The animals were divided into two groups: (1) structural muscle damage (SMD), without L-NAME infusion (SMD/−L-NAME) (n=5 at each day); (2) structural muscle damage, with L-NAME infusion (SMD/+L-NAME) (n=5 at each day). Apoptosis was assessed by Caspase-3 and Cytochrome-C assays. RESUITS: NO content was greater in the SDM/−L-NAME group at all time points (p<0.05). Three days following the bout of SMD there was greater myofiber damage and leukocyte invasion in the SMD/−L-NAME group as compared to the SMD/+L-NAME group. Both groups showed evidence for myofiber repair, however the degree of regeneration was less in the SMD/+L-NAME group. SMD/+L-NAME group compared with SMD/−L-NAME group showed a significantly higher apoptotic index in Cytochrome-C protein (p < 0.01) and Caspase-3 activity (p < 0.05), respectively. CONCLUSIONS: We conclude that NO produces an anti-apoptotic effect by suppression of caspase activity in rat skeletal muscle following a single stretch injury.