Ubiquitin–proteasome system (UPS). (A) Images of dot and western blots with representative samples for red and white muscle targeting ubiquitin and the E3 ubiquitin ligases MAFbx and MuRF1. (B) Mean expression of the UPS markers ubiquitin, MAFbx and MuRF1 within red (n=8) and white (n=8) muscle. Ubiquitin expression was significantly greater in red muscle (Student's t-test, *P<0.001) while MAFbx and MuRF1 expression was significantly greater in white muscle (Student's t-test, *P=0.03 and *P=0.005, respectively). (C) 20S proteasome activity of red (n=12) and white (n=12) muscle. 20S proteasome activity was significantly higher in red muscle (Student's t-test, *P=0.004). Data are means±s.e.m.