Modified metabolic responsiveness to glucagon in cold-acclimated and heat-acclimated rats

Calorigenic effect of glucagon on whole body oxygen consumption and interscapular brown adipose tissue (BAT) was investigated in unanesthetized and unrestrained warm controls (WC), cold-acclimated rats (CA) and heat-acclimated rats (HA). Glucagon produced significant elevation of oxygen consumption, body temperature and BAT temperature in all experimental groups. Such increased calorigenic responses to glucagon were significantly potentiated in CA and reduced in HA compared with those in WC. Thermogenic response of BAT to norepinephrine was also similar to that to glucagon; it was potentiated in CA, reduced in HA. These results indicate that glucagon would serve thermoregulatory nonshivering thermogenesis in temperature acclimation as calorigenic hormone, at least in part, through its action on BAT.