Heat production of isolated brown-fat cells by addition of noradrenaline and 
glucagon was measured in warm-acclimated control, cold-acclimated and 
heat-acclimated rats by use of a twin-type conduction microcalorimeter. 
Noradrenaline and glucagon induced maximum heat production per 10(6) cells in 
dose of 1 microgram/ml. Heat produced by maximum thermogenic response to 
glucagon was twice as much as that to noradrenaline. Thermogenic response to 
noradrenaline was markedly increased in cold-acclimated brown adipocytes, while 
it was reduced in heat-acclimated ones. Thermogenic response to glucagon was 
significantly reduced in heat-acclimated brown adipocytes, while it was not 
affected in cold-acclimated brown adipocytes.