COMPARISON OF PROTEOLYTIC VARIABLES IN A LEAN AND OBESE STRAIN OF PIGAT 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 model s. The objectives of this study were to look at proteolytic variables implicated in these processes. A lean and obese strain of swine fi om similar genetic lineage (Duroc x Yorkshire, 50:50) have been well esta blished and may prove ideal for this purpose. This study was done in t wo phases. Phase I included eight lean and eight obese pigs at 2.5 mon ths of age, and phase II was identical, but the pigs were 7 months old . Longissimus muscle samples were processed immediately after euthanas ia for activity measurements of mu-calpain, m-calpain, calpastatin, an d lysosomal cathepsins B and B + L. Additional samples were taken for DNA, RNA, and total protein determinations. In phase I, total calpasta tin activity total and specific cathepsin B + L activity, and total pr otein/g muscle were greater in the obese pigs than in the lean pigs. I n contrast, DNA and RNA/g muscle were greater in the lean pigs. No oth er differences were observed in phase I. In phase II, total calpastati n activity and total cathepsin B activity were greater in the obese pi gs 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 t he lean pigs but not in the obese pigs and calpastatin activity decrea sed in both lean and obese pigs; however, the phase-II-obese and phase -I-lean total calpastatin concentrations were not significantly differ ent. In both lean and obese pigs from phase I to phase II, mu-calpain activity, DNA/g muscle, RNA/g muscle, cathepsins B and B + L specific activity, and cathepsin B total activity/g muscle decreased. Total cat hepsin B + L activity/g muscle increased in the lean pigs from phase I to phase II, but not in the obese pigs. The data obtained in this stu dy suggest that these strains of pigs may be useful models for the stu dy of muscle and animal growth as well as skeletal muscle protein turn over