Development of nonshivering thermogenic capacity in the neonate.

为了阐明非颤抖产热(NST)的发生机制(S)，观察了去甲肾上腺素(NA)和高血糖素(G)对新生大鼠非颤抖产热个体发育的影响。棕色脂肪组织(BAT)中NA的含量在出生时很低，然后迅速增加，而G含量在出生前就已经很高，并在出生后保持在较高的水平。4%牛血清白蛋白/Krebs-Ringer磷酸盐缓冲液中的组织块在2或3小时后测定BAT的体外耗氧量。预先孵育；克拉克型氧电极)表明，NA和G在出生前就能刺激组织，出生后反应明显增强。出生前后，G反应与NA反应相同。然而，在出生后5天，G反应变小，而NA反应一直保持在高水平，直到断奶前。NA增加了蝙蝠体内的cAMP水平，这种影响在新生儿生命的后期变得更加明显。BAT cAMP的G刺激小于NA刺激，且在实验期间无明显变化。这些结果提示，在新生儿生命的早期阶段，G可能在NST中起着重要的作用，产热过程中G的激活可能涉及与NA不同的途径。研究还表明，用BAT块测量耗氧量的方法对评价BAT的NST能力是有用的。

In order to clarify the mechanism(s) of development of nonshivering thermogenesis (NST), the influence of noradrenaline (NA) and glucagon (G) on the ontogeny of NST in neonatal rats was investigated.The NA content of brown adipose tissue (BAT) was low at birth, and then increased repidly, whereas G content was already high before birth and maintained so after birth. Measurements of in vitro BAT oxygen consumption(tissue blocks in 4 % bovine serum albumin/ Krebs-Ringer phosphate buffer after 2 or 3 hr. preincubation; Clark-type oxygen electrode) showed that NA and G were capable of stimulating the tissue before birth, and the response increased markedly after birth. Around birth, the G response was same as the NA response. However, the G response became smaller by 5 days after birth, while the NA response remained in high until just before the weaning period. NA increased cAMP levels in BAT, and this effect became more marked in the later days of neonatal life. the G stimulation of BAT cAMP was smaller than the NA stimulation and showed no change over the experimental period. It was also suggested that NA as well as G increased IP_3 levels in BAT, and the responses became smaller in the later stages of neonatal life.These results suggest that G could play an important role in NST particulary in the very early period of neonatal life and that the G activation of thermogenesis may involve a different pathway from that of NA. Is was also shown that the present method for measuring oxygen consumption with BAT blocks was useful to evaluate the NST capacity of the BAT.