Changes in cathepsin D, acid autolytic activity, RNA, DNA in skeletal muscle and liver of mouse kept on high protein, carbohydrate and lipid diets.

The influence was studied of different diets on the activity of cathepsin D (PSCatD), pepstatin (PIA) and leupeptin (LIA) insensitive acid autolytic activity (AAA), RNA, DNA and protein in skeletal leg muscle (LM) and liver of 37 mice. The diets affected the weight of the liver and content of protein in the liver and LM. The protein:DNA ratio was lowest on high carbohydrate (HC) and commercial (C) diets in both tissues and about 3 times higher in LM than in the liver. The RNA:protein ratio was highest in the high protein-fat (HPF) and recommended (R) diet fed groups. The RNA:DNA ratio was lowest on HC and C diets. In the liver, PSCatD, AAA, LIA were lowest on HPF, and highest on HC diets, but for PIA on high fat-protein (HFP) and C diets, respectively. The highest activities were correlated with the lowest percentage of protein and fat in the diets (low energy diets). For LM, the highest activities were found on a C diet and lowest for PSCatD on HEP but for AAA, PIA, LIA on HC diets. Cathepsin D accounted for about 70% of hemoglobin degradation in the liver and 66% in LM. In AAA, cathepsin D participates in 58.5% and 50.5% in the liver and LM inhibition, respectively, but leupeptin accounted for about 15% and 27% (in the presence of Mg++) of inhibition.