Sarco(endo)plasmic reticulum Ca²⁺-ATPase function is impaired in skeletal and cardiac muscles from young DBA/2J mdx mice

The DBA/2J (D2) mdx mouse is a more severe model of Duchenne muscular dystrophy when compared to the traditional C57BL/10 (C57) mdx mouse. Here, we questioned whether sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA) function would differ in muscles from young D2 and C57 mdx mice. Both D2 and C57 mdx mice exhibited signs of impaired Ca²⁺ uptake in the gastrocnemius, diaphragm, and left ventricle; however, the level of impairment was more severe in D2 mdx mice. Reductions in maximal SERCA activity were also more prominent in the D2 mdx gastrocnemius and diaphragm when compared to those from C57 mdx mice; however, there were no differences detected in the left ventricle. Across all muscles, D2 mdx mice had the highest levels of oxidative stress as indicated by protein nitrosylation and/or nitration. In conclusion, our study shows that SERCA function is more impaired in young D2 mdx mice compared with age-matched C57 mdx mice.