| Abstract: | Seventy-five g Pectoralis was excised immediately post-mortem from broiler chickens and frozen in liquid nitrogen. A linear gradient (0- 500 mM NaCI) eluted two peaks of calcium-activated neutral proteolytic activity from a DEAE-anion exchange column. One required approximately 100 μM Ca[^2+] for half-maximal activity and the other approximately 500 μM Ca[^2+]. SDS-PAGE revealed that enzymes were not pure. Calpain and calpastatin activities were examined in broiler tissues with different cellular turnover rates. Avian brain (B), cardiac muscle (C), kidney (K), liver (L), Pectoralis (P), and small intestinal mucosa (SMI) were collected at 9 wk post-hatch and immediately extracted. A linear gradient (25-200 mM NaCI) eluted calpain I from DEAE-anion exchange column; subsequent washing with 400 mM NaCI eluted calpain II. C, K, L, P, and SMI had substantial calpain II activity; B had moderate levels. L, P, and SMI had detectable calpain I levels, but lower than calpain II. B had the lowest detectable calpain I activity. Calpastatin activity was quantified in broiler B, C, K, L P, and SMI at 1 d, 7 wk, and 12 wk post-hatch. Three 10 g tissue pools were extracted immediately post-mortem. Calpastatin activity was greatest at 1 d and decreased thereafter for all tissues except B, where it remained constant. Within age, activity was consistently highest in SMI and C, intermediate in B, L, and K. Activity in P declined 7-fold by 7 wk. Fast-growing broiler and slow-growing Leghorn chickens were used to compare Pectoralis calpain and calpastatin activities at 1, 11 and 21 d post-hatch. Calpastatin activity did not differ between strains at any sampling time. Calpastatin activity was highest at 1 d, declined by 11 d and remained low at 21 d. Calpain I activity did not differ between strains at any sampling time. Calpain I activity was lowest in both strains at 1 d, increased at 11 d and remained high at 21 d. Calpain II activity did not differ between strains for any sampling time; calpain II activity was highest at 1 d, decreased slightly at 11 d and remained low at 21 d. Calpain II activity was higher than that of calpain I for both strains at all sampling times. |
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