COMPARISON OF INVITRO THERMOGENESIS OF BROWN ADIPOSE-TISSUE IN COLD-ACCLIMATED RATS AND GUINEA-PIGS

1. Effects of noradrenaline (NA) and glucagon (G) were investigated on in vitro brown adipose tissue (BAT) thermogenesis by measuring oxygen consumption with an oxygen electrode on finely minced tissue blocks incubated in Krebs-Ringer phosphate buffer at 37-degrees-C. 2. The interscapular BAT weight increased in rats, while it rather decreased in guinea pigs by cold acclimation. Fat percentage in BAT decreased in the cold-acclimated rats and guinea pigs. 3. NA- and G-stimulated oxygen consumptions of BAT expressed per mg tissue weight were suppressed in the cold-acclimated rats, but were enhanced in the cold-acclimated guinea pigs as compared with those in the warm control animals. Adenosine deaminase did not affect the result in the cold-acclimated rats. However, the oxygen consumption per BAT pad did not differ between the cold-acclimated and warm control animals. 4. These findings reveal species differences in the in vitro responsiveness of BAT of cold-acclimated animals to the thermogenic factors. It is further suggested that some compensatory mechanisms such as hyperplasia and/or increased blood flow induce an enhanced thermogenesis in BAT during cold acclimation.