In vitro energy costs of NA+, K+ATPase activity and protein synthesis in muscle from calves differing in age and breed

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Abstract
1. An in vitro preparation was used to measure rates of oxygen consumption, Na+, K+-ATPase-dependent respiration, [14C]phenylalanine incorporation and tyrosine release of skeletal (stenomandibularis) muscle from 10-21 -d-old (three) and 7-month dairy (three) calves and control (CDM; four) and extreme double-muscled (EDM; two) calves.2. Rate of oxygen consumption was greatest (P< 0.001) for muscle from 10.21-d-old dairy calves and lowest (P< 0.05) for CDM calves.3. Ouabain (10−6M) caused a 40% inhibition of muscle respiration.4. Na+, K+-ATPase-dependent respiration was similar for muscle from all calf groups except 10-21-d-old dairy calves which had a value 26% greater (P< 0.001) than that of older dairy calves.5. Na+, K+-ATPase-independent respiration was 16% greater (P< 0.001) for muscle from 10.21-d-old than that of older dairy calves while muscle from EDM calves had a value 11 % greater than that of CDM caives.6. The rate of [14C]phenylalanine incorporation was greater (P< 0.05) for muscle from 10-21-d-old dairy than from older dairy calves, similar between older dairy and CDM calves, and decreased (P< 0.05) for EDM calves.7. Rate of tyrosine release was greatest (P< 0.05) for muscle from CDM and EDM calves: both dairy groups had similarly low rates of muscle tyrosine release.8. The energy estimated to be required for peptide bond synthesis accounted for 2.0–3.3% of the O2consumption of the muscle preparations.