In vitro Na+, K+-ATPase (EC 3.6.1.3)-dependent respiration and protein synthesis in skeletal muscle of pigs fed at three dietary protein levels

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Abstract
1. Eighteen pigs were offered diets containing 130, 170 or 210 g protein/kg with three barrows and three gilts per diet from 20 to 60 kg live weight. Oxygen consumption, Na1, K1-ATPase (EC3·6·1· 3)-dependent and -independent respiration and protein synthesis were measured in vitro in intercostal and sartorius muscle preparations from these pigs.2. Increasing dietary protein concentration increased (P< 0·01) daily gain and dissectible muscle in carcass.3. O2consumption and Na+, K+-ATPase-dependent respiration of the intercostal and sartorius muscles increased linearly (P< 0·01) with increase in dietary protein concentration. The requirement for the support of the transport of Na+and K+across the cell membrane in these muscles, on average, accounted for 22–25% of the O2consumption.4. Synthesis rate (mg/g per d) of protein in the sartorius muscle increased (P< 0·05) from 3·05 to 5·07 and increased (P< 0·1) from 2·57 to 4.06 in the intercostal muscle as dietary protein increased from 130 to 210 g/kg diet.5. Regression of Na+, K+-ATPase-dependent respiration against protein synthesis in each of intercostal and sartorius muscles showed a linear relation, an attestation of a close link between productive processes and auxiliary energy expenditure.