Comparison of proteolytic variables in a lean and obese strain of pig at the ages of 2.5 and 7 months.

The mode(s) of skeletal muscle protein turnover as well as muscle and animal growth may be studied by using lean and obese animals as models. The objectives of this study were to look at proteolytic variables implicated in these processes. A lean and obese strain of swine from similar genetic lineage (Duroc x Yorkshire, 50:50) have been well established and may prove ideal for this purpose. This study was done in two phases. Phase I included eight lean and eight obese pigs at 2.5 months of age, and phase II was identical, but the pigs were 7 months old. Longissimus muscle samples were processed immediately after euthanasia for activity measurements of mu-calpain, m-calpain, calpastatin, and lysosomal cathepsins B and B + L. Additional samples were taken for DNA, RNA, and total protein determinations. In phase I, total calpastatin activity, total and specific cathepsin B+L activity, and total protein/g muscle were greater in the obese pigs than in the lean pigs. In contrast, DNA and RNA/g muscle were greater in the lean pigs. No other differences were observed in phase I. In phase II, total calpastatin activity and total cathepsin B activity were greater in the obese pigs than in the lean pigs. No other differences were observed in phase II. From phase I to phase II, mu-calpain total activity increased in the lean pigs but not in the obese pigs and calpastatin activity decreased in both lean and obese pigs; however, the phase-II-obese and phase-I-lean total calpastatin concentrations were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)