Resting metabolism in hypoxia-acclimated rats during acute hypoxic exposure

In contrast to the decreased metabolism in non-hypoxia-acclimated (CT) rats, acute hypoxia (9.5% O2) did not change the resting metabolism in hypoxia-acclimated (HX: 12% O2 for 2 months) rats at 25 degrees C. After beta-adrenergic blockade, acute hypoxia greatly reduced the resting metabolism in HX rats. The calorigenic response to norepinephrine (0.4 mg . kg-1) during acute hypoxia was, however, identical with that observed in CT rats. These results suggest an enhanced beta-adrenergic stimulation in HX rats during acute-exposure to hypoxia.