Post-natal development of brown adipose tissue in the rat bred at 23 degrees C or 28 degrees C

Effect of ambient temperature on the proliferation of brown adipocyte progenitors and endothelial cells during postnatal BAT development in Syrian hamsters

In Syrian hamsters, brown adipose tissue (BAT) develops postnatally through the proliferation and differentiation of brown adipocyte progenitors. In the study reported here, we investigated how ambient temperature influenced BAT formation in neonatal hamsters. In both hamsters raised at 23 or 30 °C, the interscapular fat changed from white to brown coloration in an age-dependent manner and acquired the typical morphological features of BAT by day 16. However, the expression of uncoupling protein 1, a brown adipocyte marker, and of vascular endothelial growth factor α were lower in the group raised at 30 °C than in that raised at 23 °C. Immunofluorescent staining revealed that the proportion of Ki67-expressing progenitors and endothelial cells was lower in the 30 °C group than in the 23 °C group. These results indicate that warm ambient temperature suppresses the proliferation of brown adipocyte progenitors and endothelial cells and negatively affects the postnatal development of BAT in Syrian hamsters.

Serotonin level and turnover rate in brown adipose tissue of developing rats

The level and turnover rate (TR) of serotonin (5-HT) were determined in the brown adipose tissue (BAT) of rats born and reared at 28 degrees C and 16 degrees C. The serotonin/norepinephrine ratio was high in BAT of both groups for the first 2 days. Thereafter it fell. During the first 3 days, the TR was three times higher in 16 degrees C rats than in 28 degrees C rats. A similar difference was observed for the 5-HIAA/5-HT ratio during that period. It is concluded that 5-HT may act on BAT thermogenesis in cold-exposed pups but its mechanism of action is still hypothetical.