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

Abstract

1. An in vitro preparation was used to measure rates of oxygen consumption, Na + , K + -ATPase-dependent respiration, [ 14 C]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 −6 M) 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 [ 14 C]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 O 2 consumption of the muscle preparations.