Calorigenic effect of glucagon and catecholamines in king penguin chicks

Abstract
The calorigenic action of glucagon and catecholamine infusion was evaluated in winter-acclimatized king penguin chicks at 20.degree. and 0.degree. C ambient temperature (Ta). At Ta = 20.degree. C the mean increase in metabolic rate was 0.73 W .cntdot. kg-1 for epinephrine (80 .mu.g .cntdot. kg-1), 0.42 W .cntdot. kg-1 for norepinephrine (150 .mu.g .cntdot. kg-1), and 1.16 W .cntdot. kg-1 for glucagon (0.75 .mu.g .cntdot. kg-1); i.e., respectively 30, 17 and 47% of the control value. The maximum response to glucagon reached 89% over control. At Ta = 0.degree. C, for the same glucagon infusion, the mean increase in specific metabolic rate was 0.84 W .cntdot. kg-1, 27% of control rate. In the cold, glucagon infusion inhibited shivering and substituted its calorigenic action, resulting in a less apparent effect. In contrast with the negligible effect of catecholamines, glucagon infused at low doses exerted a powerful calorigenic action in young king penguins and could be considered as a possible nonshivering thermogenesis mediator.

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