Energy costs of ion pumping by animal tissues
Milligan, L.P.; McBride, B.W.
Journal of Nutrition 115(10): 1374-1382
1985
ISSN/ISBN: 0022-3166 PMID: 2413191 Document Number: 266583
Results from recent studies in vitro indicate that in excess of 20% of the energy expenditure of skeletal muscle, duodenal epithelium and liver of domestic ruminants is to achieve sodium+ and potassium+ transport across the plasma membrane. The energy cost of active calcium2+ transport is less clear but is likely less than 10% of the total expenditure of skeletal muscle at rest. Energy expenditure on Na+ and K+ transport was quite sensitive to the physiological state of the animal. During lactation, Na+ and K+ transport accounted for nearly half of the uptake in vitro of skeletal muscle, duodenal epithelium and liver. The energetic cost of supporting Na+ and K+ transport was also greater in young than in older animals, by feed intake and by exposure to cold. Na+ and K+ transport seems to be a substantial component of the maintenance energy expenditure of ruminant tissues. Its variation, therefore, implies that change of maintenance energy expenditures with physiological state of the animal warrants serious attention.