Oxidative metabolism of isolated foetal and neonatal rabbit brown adipose tissue. III. The effect of isoprenaline-induced lipolysis

Abstract

The brown adipose tissue (BAT) is the site of thermogenesis in the neonatal and the hibernating mammal. In the neonatal rabbit, cold exposure induces an increase in oxygen uptake and heat production by the BAT (Dawkins & Hull, 1964). BAT is a strongly innervated tissue (Cottle & Cottle, 1970) and its noradrenaline content is high (Sidman et al., 1962). In neonatal rabbits, noradrenaline infusion produces the same effect as cold exposure (Dawkins & Hull, 1964). It has therefore been concluded that noradrenaline is the physiological mediator of the cold. Noradrenaline induces lipolysis and the increase in intracellular free fatty acids leads to uncoupling of the oxidative phosphorylations and to a subsequent heat production (Hittelman & Lindberg, 1970; Wojtczak, 1974). The aim of our study was to assess the maturation of the BAT during the last days of foetal development, by mimicking in vitro the effects of cold exposure with the β-adrenergic agent isoprenaline.