Really does temperature reduction and norepinephrine have similar effects on the energy metabolism in rat brown adipose tissue?

Context: Heat generation by brown adipose tissue (BAT) in response to temperature reduction seems to be entirely related to sympathetic nervous stimulation.Objective: To analyse if temperature reduction and norepinephrine may differently affect the expression of proteins related to energy metabolism in BAT.Materials and methods: Isolated rats BAT was incubated with/without norepinephrine (10–6 mol/L, 24 h at 32 °C and 37 °C).Results: In BAT, 32 °C increased the protein expression levels of carnitine palmitoyltransferase-I and -II, mitochondrial uncoupling protein-1 (UCP-1) and the expression and activity of lactate dehydrogenase. Mitochondrial F1-ATP synthase α-chain expression was decreased at 32 °C compared to 37 °C. Norepinephrine and at 32 °C exposure, UCP-1 expression was increased but cytochrome-c oxidase and F1-ATP synthase α-chain expression was reduced with respect to 37 °C.Discussion: Sympathetic stimulation seems not to be the only factor associated with heat generation.Conclusions: Temperature reduction by itself exerts some different effects on the expression of proteins related to the energy metabolism than norepinephrine.