Studeis on regulating factors for function and proliferation of thermogenic tissue, brown adipose tissue.

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Roles of pancreatic hormone, glucagon, and membrane glycolipid, gangliosides, in the regulation of thermogenic tissue, brown adipose tissue, were studied in rat1. Glucagon level in brown adipose tissue (BAT) was 3 to 4 times higher than that in plasma. It was significantly higher in the dorsocervical site than in the interscapular site. Cold acclimation, acute cold exposure and non-thermal stress (acute immobilization) all elevated BAT glucagon.2. Noradrenaline, a major enhancing factor of non-shivering thermogenesis (NST), elevated glucagon level in plasma as well as in BAT. The extent of elevation of plasma glucagon was greater in the cold-acclimated animals (CA) than warm controls (WC).3. In vivo thermogenic responses to noradrenaline and glucagon were enhanced in BAT as well as whole body in CA. On the other hand, in vitro oxygen consumption of BAT was significantly reduced in CA. However, it was significantly greater in the cold-acclimated guinea-pig. Adenosine deaminase did not influence the reduction in hormone-induced oxygen consumption of BAT from CA.4. Repetitive short-term cold exposure elicited the same cold adaptability as that induced by continous exposure with one-fourth of time of continous cold exposure. This type of cold acclimation was also accompanied by the elevated glucagon level of BAT.5. Ganglioside GM_3 was found to be a major ganglioside in BAT. Cold acclimation and successive rearing in cold caused significant elevation of ganglioside GM_3 in BAT. GM_3 level was also higher in BAT of 4- and 14-day old rats than in BAT 11-week old adults. These results suggest that glucagon and GM_3 play as regulating factors for proliferation as well as function of BAT.