The effect of forced running on heat production in brown adipose tissue in rats.

The effect of running on heat production in brown adipose tissue (BAT) was compared between trained and untrained rats. Rats were forced to run a treadmill while temperatures of colon (T col) and interscapular BAT (T bat) were measured. The daily running for 5 weeks neither changed the size of interscapular BAT nor the norepinephrine-induced thermogenesis (8 micrograms/kg X min). During running, both T bat and T col increased. In rats trained for 2 weeks, the increases in T bat were similar to those in T col. In untrained rats, however, the increases in T bat were larger than those in T col. It is suggested that exercise increases heat production in BAT in untrained rats, but such heat production in BAT is abolished by daily exercise. Exercise suppresses cold-induced heat production in BAT of trained rats.