Abstract
To elucidate the mechanism of brown adipose tissue (BAT) enlargement during cold exposure, we investigated the effects of BAT extracts and blood plasma on the growth of brown adipose cells and capillary growth in vitro in rats. BAT and blood were collected from male Wistar strain rats maintained at 25°C (warm-adapted, WA) or 5°C (cold-acclimated, CA) for 4 weeks. The BAT extracts of both WA and CA rats markedly increased the growth of rat brown adipose cells and bovine capillary endothelial cells, there being no definite difference in the effects. On the other hand, the plasma of CA rats significantly increased the growth of these cells compared to that of WA rats. Moreover, the effect of plasma addition on the capillary growth in vitro was considerably greater in CA rats than in WA rats. These results suggest that plasma from CA rats contains some growth factor (s) in the BAT enlargement and that there is an intimate connection between capillary growth and BAT enlargement.
