It is well known that rapid gain of muscle mass in neonatal pigs is highly related to protein synthesis. However, the role of protein degradation in muscle gain of the neonatal period has not been well established. Calpains and their endogenous inhibitors, calpastatins, play a significant role in early-stage myofibrillar protein degradation. To investigate the role of calpain-calpastatin system in muscle protein accumulation, we studied the expressions of their mRNA in muscle tissue sampled at days 1, 4, 6, 12, 20 and 28 from a total of 36 neonatal pigs. The steady-state mRNA levels of calpains 1A, 2 and 3A, calpastatin types 1, 2 and 3, obtained by quantitative real-time PCR analysis, decreased by 2-4 folds at the age of 4 to 6 days compared to 1-day-old piglets. Then, the relatively low expression level was maintained through 28 days of age. Expressions of calpains 1A, 3A and calpastatin type 1 were significantly correlated with the measurements of muscle protein accumulations such as muscle protein content and RNA/protein ratio. Expressions of calpain 1A, calpastatin types 1 and 3 were negatively correlated with birth weight and fractional rate of growth. The levels of calpains 1A and 2 mRNA were correspondent to their protease activities. In conclusion, decreased levels of calpain and calpastatin expressions over development in neonatal pigs are associated with high protein accumulations, suggesting that dramatic muscle growth during the neonatal period may be partially controlled by down-regulated calpain-calpastatin system.
|Original language||English (US)|
|Number of pages||6|
|Journal||Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology|
|State||Published - Apr 2009|
Bibliographical noteFunding Information:
This work was supported by research grants from the USDA Hatch project (HAW00268-R), USDA-CSREES (TSTAR Award #2008-34135-19322), Hawaii Farm Bureau Federation and Department of Agriculture of Hawaii (Award # 20070992). We are grateful to Dr. Ching Yuan Hu and Dr. Le Ann Blomberg for their comments on the manuscript.
- Neonatal pigs
- Protein deposition
- Skeletal muscle