In the rat proximal tubule, 2B-adrenergic receptor (2B-AR) enhances Na+-reabsorption by increasing NHE3 activity. The mechanisms involved are unclear and inhibition of cAMP production remains controversial. In this study, we reinvestigated 2B-AR signaling pathways using rat proximal tubule cells in primary culture (PTC) and LLC-PK1 cells permanently transfected with the RNG gene (rat non-glycosylated 2-AR). Binding experiments indicated that PTC express substantial amounts of 2B-AR (130 fmol/mg of proteins), and only RNG transcripts were detected. In both cell types, the 2B-AR is coupled to G-protein and its stimulation by dexmedetomidine, but not by UK14304, provoked a significant inhibition of the accumulation of cAMP induced by forskolin or PTH. Exposure to 2-agonists increased arachidonic acid release and caused ERK1/2 phosphorylation, which correlated with enhanced MAPK activity and nuclear translocation. MAPK phosphorylation was blunted by pertussis toxin but not by PKC desensitization and it coincided with transient phosphorylation of Shc. Finally, treatment with UK14304 accelerated cell growth. Further studies will be necessary to clarify the precise mechanism of MAPK activation, but the present data suggest that 2B-AR may play a positive role during tubular regeneration.