Original Article AMP-Activated Protein Kinase Activation by Adrenoceptors in L6 Skeletal Muscle Cells Mediation by 1-Adrenoceptors Causing Glucose Uptake

AMP-activated protein kinase (AMPK), which functions as a sensor of cellular energy homeostasis, was phosphory-lated after norepinephrine stimulation in L6 skeletal mus-cle cells. This effect was mediated by 1-adrenoceptors, with no stimulatory effects due to interactions at 2- or -adrenoceptors. 1-Adrenoceptors are Gq-coupled recep-tors, and calcium but not phorbol esters could mimic the effect of 1-adrenergic stimulation; and we show that pro-tein kinase C is not involved as an upstream signal to AMPK by 1-adrenergic stimulation and that the AMP-to-ATP ratio is unaltered after 1-adrenergic stimulation. We further show that glucose uptake mediated by 1- but not by -adrenoceptors can be inhibited by AMPK inhibition. Acetyl-CoA carboxylase (ACC) is phosphorylated at Ser218 by AMPK, and 1- but not -adrenoceptor stimula