Parallel measurements of heat production and thermogenin content in brown fat cells during cold acclimation of rats.

The maximum thermogenic capacity of brown fat cells from control and cold acclimated rats was measured using a continuous-flow microcalorimetric system. The content of the 32.000 D, brown fat specific protein, thermogenin, was measured in the cells used for heat production measurements by competitive ELISA. The ratio between the maximal thermogenic capacity and the amount of thermogenin for control and cold acclimated rats was compared. It was found that the ratio between the two parameters decreased during cold acclimation due to a decrease in maximal thermogenic capacity and an increase in the amount of thermogenin, indicating regulation of heat production either at thermogenin or receptor level.