Functional correlates of Na+,K+-ATPase in lean and obese (ob/ob) mice

Concentrations of Na+,K+-ATPase enzyme units are lower in skeletal muscle and liver of adult obese (ob/ob) mice than in their lean counterparts. The present studies were designed to provide information on functional correlates of Na+,K+-ATPase in ob/ob mice. Obese mice had lower potassium (K+) content in muscle and liver and higher sodium (Na+) content in muscle and liver and higher sodium (Na+) content in muscle than lean counterparts. The calculated intracellular Na+/K+ ratio in muscle of obese mice was approximately twice as high as in muscle of lean mice. Oxygen consumption was measured in mice maintained at 14 degrees, 25 degrees, or 33 degrees for 40 min and injected with 0.3 or 0.9 microgram ouabain per g body weight. Ouabain, a specific inhibitor of Na+,K+-ATPase, decreased oxygen consumption less in obese mice (12%--25%) than in lean mice (19%--38%). These results suggest that Na+ pump activity may be reduced in obese mice.