Skeletal muscle and liver protein degradation in mice divergently selected for low and high body weight over 108 generations

Abstract. Experiment was carried out on 111 and 13-14 weeks old mice divergently selected for low (L) and high (C) body weight over 108 generations. In leg muscle and liver cathepsin D (CatD) was determined as pepstatin sensitive activity (PSCatD), and as pepstatin-insensitive (PIA) and leupeptin-insensitive (LIA) acid autolytic activities (AAA) were measured. In leg muscle and liver all measured activities were higher in L as compared to C and control (K) mice. The percent of inhibition of LIA was lower in L then C mice in both examined tissues. In the leg muscles, in L mice protein catabolism was mostly influenced by CatD, but in the liver CatD was mostly active in K mice. CatD, PSCatD, AAA and LIA in leg muscle of L mice as compare to K were higher in female (F) by 68 %, 68.5 %, 91.3 % and 94.5 %, respectively, and in male (M) mice by 43.4 %, 54 %, 47.1 % and 64 %, respectively. The percent of inhibition by leupeptin in AAA was higher in C mice by 61.9 % in F and by 40 % in M mice. In the liver, PIA was higher by about 45 % in L and by 28.5 % in C mice as compare to K ones. There were about 36% of 30.00-39.99 μm muscle fibrils in M mice and in males of L group 40.00-49.99 μm fibrils appeared at 25% (absent in 3 weeks mice). In female, all measured fibril diameters were in higher percent in L than in C group. RNA variables were higher by about 25% (in average) in C as compare to K and L groups. Functional cell size (FCS) was lowered in L and C group as compared to K by about 10 % (in average). These results indicate on faster proteins turnover in L than in C group of mice.