Induction of type II iodothyronine 5'-deiodinase and mitochondrial uncoupling protein in brown adipocytes differentiated in cell culture.

Brown adipocytes differentiated in primary cell culture were found to contain a type II iodothyronine 5'-deiodinase (5'D). Incubation of confluent cells with norepinephrine or dibutyryl-cAMP caused up to 17-fold increase in 5'D activity with a maximum after 8 h. Activation of 5'D required mRNA and protein synthesis and was accompanied by parallel, up to 5.8-fold increase in the amount of mitochondrial uncoupling protein with a maximum after 24 h. Analysis of adrenergic stimulation of 5'D suggested predominant involvement of the beta-receptors and increased intracellular cAMP levels, while the contribution of alpha 1-receptors was small.