Relationship between body size, Na+-K+-ATPase activity, and membrane lipid composition in mammal and bird kidney.
We investigated the relationship between body size, Na(+)-K(+)-ATPase molecular activity, and membrane lipid composition in the kidney of five mammalian and eight avian species ranging from 30-g mice to 280-kg cattle and 13-g zebra finches to 35-kg emus, respectively. Na(+)-K(+)-ATPase activity was found to be higher in the smaller species of both groups. In small mammals, the higher Na(+)-K(+)-ATPase activity was primarily the result of an increase in the molecular activity (turnover rate) of individual enzymes, whereas in small birds the higher Na(+)-K(+)-ATPase activity was the result of an increased enzyme concentration. Phospholipids from both mammals and birds contained a relatively constant percentage of unsaturated fatty acids; however, phospholipids from the smaller species were generally more polyunsaturated, and a complementary significant allometric increase in monounsaturate content was observed in the larger species. In particular, the relative content of the highly polyunsaturated docosahexaenoic acid [22:6(n-3)] displayed the greatest variation with body mass, scaling with allometric exponents of -0.21 and -0.26 in the mammals and birds, respectively. This allometric variation in fatty acid composition was correlated with Na(+)-K(+)-ATPase molecular activity in mammals, whereas in birds molecular activity only correlated with membrane cholesterol content. These relationships are discussed with respect to the metabolic intensity of different-sized animals.
Turner
Nigel
N
Metabolic Research Centre, Department of Biomedical Science, University of Wollongong, Wollongong, New South Wales 2522, Australia. nigelt@uow.edu.au
Haga
Kurt L
KL
Hulbert
A J
AJ
Else
Paul L
PL
D000818:Animals; D001481:Basal Metabolism / Q000502:physiology; D001717:Birds / Q000378:metabolism / Q000502:physiology*; D049628:Body Size / Q000502:physiology*; D005229:Fatty Acids, Monounsaturated / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D007668:Kidney / Q000201:enzymology*; D016014:Linear Models; D008322:Mammals / Q000378:metabolism / Q000502:physiology*; D008563:Membrane Lipids / Q000737:chemistry*; D008861:Microsomes / Q000201:enzymology; D009929:Organ Size / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013045:Species Specificity
D005229:Fatty Acids, Monounsaturated; D005231:Fatty Acids, Unsaturated; D008563:Membrane Lipids; D000254:Sodium-Potassium-Exchanging ATPase