EFFECTS OF AGE AND TISSUE-TYPE ON THE CALPAIN PROTEOLYTIC SYSTEM IN TURKEY SKELETAL-MUSCLE

A study was conducted to examine the effects of bird age and muscle ti ssue type on calpain and calpastatin activities in turkey skeletal mus cle. Enzymatic activities of calpains and calpastatin were found to va ry with bird age and muscle type. Breast muscle from younger birds (ag e 5 wk) had higher mu-calpain, m-calpain, and calpastatin activities ( P < 0.05) than breast muscle from older birds (9, 13, and 17 wk of age ). Thigh muscle calpain activities were not affected by bird age, but thigh calpastatin activity was found to increase with age, with muscle from 17-wk-old birds having 35% higher activity than muscle from 13-w k-old birds. When extracted from 9-wk-old turkeys, breast muscle mu-ca lpain activity was 30% higher than thigh muscle mu-calpain. By 13 wk o f age, breast muscle mu-calpain activity was 20% less than thigh mu-ca lpain. Thigh muscle m-calpain and calpastatin activities were found to be significantly higher (P < 0.05) than that found in breast muscle, with some values more than double in older birds (17 wk of age).