| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1992: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1991: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
In order to clarify the thermogenic mechanisms of brown adipose tissue (BAT),main site of nonshivering thermogenesis (NST), the effects of noradrenaline (NA), glucagon (G) and beta-3 adrenergic agonist (BRL37344:BRL) on in vivo and in vitro thermogenic activities of BAT under various conditions were examined and the following results were obtained. 1. Cold-adapted rats for successive generations had high nonshivering thermogenic capacity,but they seem to be adapted to cold under less energy expenditure compared with cold-acclimated rats(CA). 2. Female rats had same thermogenic capacities as male ones in both criteria of in vivo and in vitro. 3. In CA, GDP-binding to BAT mitochondria was significantly high after acute cold exposure, although it was not different from WC in the resting state. While those in intermittently cold-exposed rats (ICE) were significantly high than those of WC in the both conditions. 4. In spite of the high thermogenic capacities in vivo, the in vitro BAT themogenic activity was suppressed in CA, possibly through some inhibition(s) on the post-cAMP signalling system. There were no differences among the effects of NA, G and BRL. 5. The positive relationship between lipolysis and increase in oxygen consumption of BAT was observed only in ICE. 6. Chronic administration of NA, but not of G, simulated the in vitro BAT responses to thermogenic the above agents. 7. IP_3 stimulated thermogenesis in BAT of the early stage of neonatal life. 8. The responses of BAT to isoprenaline, G and BRL were suppressed under hypothyroidism. 9. These results indicate that BAT thermogenic capacity could be modified differently under different conditions, that G stimulates BAT thermogenesis, in part, via IP_3 route, and that the thermogenic activity of brown adipocyte could be suppressed under cold acclimation, provably to prevent overworking under continuous NA stimulation.
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