Nonshivering thermogenesis in king penguin chicks. II. Effect of fasting

penguin chicks. I. Role of skeletal muscle. Am. J. Physiol. 261 (Regulatory Integrative Comp. Physiol. 30): R1438-R1445, 1991.-In cold-acclimatized (CA) king penguin chicks exhibit-ing nonshivering thermogenesis (NST), protein content and cytochrome oxidase (CO) activity of tissue homogenates were measured together with protein content, CO, and respiration rates of isolated mitochondria from skeletal muscle (gastroc-nemius and pectoralis) and liver. The comparison was made with chicks reared at thermoneutrality (TN) for at least 3 wk. In CA chicks showing a NST despite the lack of brown adipose tissue, an increase in thermogenic capacity was observed in skeletal muscle in which the oxidative capacity rose (+28 % and +50 % in gastrocnemius and pectoralis muscles, respectively), whereas no change occurred in the liver. Oxidative capacity of skeletal muscle increased together with the development o