Temperature adaptation and brown adipose tissue in hairless and albino mice

Abstract

Genetically hairless and furred albino mice were chronically exposed to 7, 10, 21, 30, 35 or 37.5 °C ambient temperature. After four weeks of adaptation brown adipose tissue (BAT) was dissected from different cervicothoracic regions, weighed, and examined histologically. At 30 °C both hairless and albino mice had minimal amounts of BAT, however, hairless mice had 19% more BAT than albinos. Cold adaptation caused a maximum 145% increase of BAT weight in albino mice and 185% increase in hairless mice. Heat adaptation also increased BAT weight, but the heat induced increase was greater in albinos than in hairless mice. Because of this similar effect of heat and cold it is concluded, that growth of BAT is controlled proportional to the severity of thermal stress. The histological appearance of BAT cells from cold adapted and from heat adapted mice is completely different. Cold adaptation caused development of metabolically active, multilocular BAT cells. Heat adaptation caused development of unilocular BAT cells with only a small content of cytoplasm. Therefore, a further mechanism is assumed which is responsible for differentiation between cold specific BAT cells or heat specific BAT cells during the cold or heat induced growth of BAT.