Catabolic metabolism provides the energy (ATP) that is essential for normal organism function, and in endotherms it also produces heat necessary for thermoregulation. However, many birds and mammals do not regulate their body temperature metabolically during development, even after birth or hatching. We are investigating changes in enzyme kinetics and gene expression to understand the development of metabolic capacity and, hence, endothermy during the early ontogeny of birds.
For example, during ontogeny in the chicken there are significant changes in the activity of cytochrome c oxidase (COX), an enzyme that regulates aerobic capacity (A). At the same time, COX gene expression is significantly upregulated compared to adults, and compared to a housekeeping gene (POLR2E; B).
Seebacher, F., Schwartz, T. A., Thompson, M. B. 2006. Transition from ectothermy to endothermy: the development of metabolic capacity in a bird (Gallus gallus). Proceedings of the Royal Society B 273, 565-570.