|Budget Amount *help
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1988: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1987: ¥1,800,000 (Direct Cost: ¥1,800,000)
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.