Abstract
Previous studies have shown that neural stimulation of brown adipose tissue (BAT) reorganizes the expression and activity of signaling proteins in the β-adrenergic adenylyl cyclase pathway. Cold stress increases neural stimulation of BAT and increases α1-adrenergic receptor number; however, the α1 receptor subtype involved and the mechanism of up-regulation by cold stress have not been determined. Using reverse transcription/polymerase chain reaction analysis and nuclease protection assay, BAT was demonstrated to express mRNAs encoding α1a and α1d, but not α1b, receptors. Parallel pharmacologic studies of BAT membranes and recombinant α1a and α1d receptors expressed in COS-7 cells demonstrated that α1a receptors predominate in BAT. Exposure of rats to 4° for 4 days increased α1a receptors and mRNA in BAT but did not alter expression of α1d receptors or mRNA. The induction of α1a receptor and mRNA level by cold stress was prevented by selective surgical denervation of BAT. Furthermore, α1a receptor and mRNA expression could be induced in warm-adapted rats by infusions of the selective β3-adrenergic receptor agonist CL 316,243. These data indicate that neural activation of β3-adrenergic receptors is an important determinant of α1a adrenergic receptor expression in BAT.
- The American Society for Pharmacology and Experimental Therapeutics
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