Accumulation of nitrotyrosine on the SERCA2a isoform of SR Ca-ATPase of rat skeletal muscle during aging: A peroxynitrite-mediated process?

The SR Ca-ATPase in skeletal muscle SR vesicles isolated from young adult (5 months) and aged (28 months) rats mas analyzed for nitrotyrosine. Only the SERCA2a isoform contained significant amounts with approximately one and four nitrotyrosine residues per young and old Ca-ATPase, respectively. The in vitro exposure of SR vesicles of young rats to peroxynitrite yielded selective nitration of the SERCA2a Ca-ATPase even in the presence of excess SERCA1a. No nitration was observed during the exposure of SR vesicles to nitric oxide in the presence of O-2. These data suggest the in vivo presence of peroxynitrite in skeletal muscle, The greater nitrotyrosine content of SERCA2a from aged tissue implies an age-associated increase in susceptibility to oxidation by this species.