Induction of iNOS paralleled attenuated IR- and IRS-1-mediated insulin signaling in skeletal muscle after burn injury in wild-type mice. A, Immunoblotting (IB) revealed a robust induction of iNOS expression at 3 days after burn injury. The protein expression of GAPDH was not altered following burn injury. B, C, D, Before (0) or at 1, 3 and 7 days after burn injury, insulin (5 U/kg BW) was injected and muscle was excised 90 sec thereafter. Immunoprecipitation (IP) followed by immunoblotting demonstrated that insulin-stimulated tyrosine phosphorylation (PY) of IR and IRS-1 was significantly decreased at 3 days after burn injury. The protein expression of IR was unaltered by burn injury. In contrast, IRS-1 protein expression was significantly decreased at 3 and 7 days after burn injury as compared with before burn injury. E, The ratio of insulin-stimulated IRS-1 phosphorylation normalized to IRS-1 protein expression was significantly decreased at 3 days after burn injury. *P<0.05, **P<0.01 vs before burn injury. n = 3 per group.