Na+ pump activity and nuclear T3 receptors in tissues of genetically obese (ob/ob) mice.

A dramatic reduction in ouabain-sensitive tissue respiration of obese mouse muscle and liver was observed, suggesting that Na+-transport-dependent calorigenesis is impaired in these animals. Additionally, a significantly depressed nuclear triiodothyronine binding capacity in liver and lung tissue was exhibited by obese mice. These data support the suggestion that the hypometabolism and hypothermia of the genetically obese mouse is a result of reduced Na+-pump-related thermogenesis; and further, provides evidence that this may be the consequence of reduced nuclear binding of triiodothyronine.