Adenosine 3′-monophosphate (3′-AMP) is a metabolite produced from hydrolysis of 2′,3′-cAMP by a family of metal-dependent phosphodiesterases. 3′-AMP inhibit proliferation of preglomerular vascular smooth muscle cells and glomerular mesangial cells via A2B receptors. 2′,3′-cAMP and 3′-AMP represent a new unexplored pathway for adenosine-based cell regulation.