Extracellular nucleotides regulate cellular functions of podocytes in culture

Abstract

Extracellular nucleotides are assumed to be important regulators of glomerular functions. This study characterizes purinergic receptors in podocytes. The effects of purinergic agonists on electrophysiological properties and the intracellular free Ca2+ concentration of differentiated podocytes were examined with the patch-clamp and fura 2 fluorescence techniques. mRNA expression of purinergic receptors was investigated by RT-PCR. Purinergic agonists depolarized podocytes. Purinergic agonists similarly increased intracellular free Ca2+ concentration of podocytes. The rank order of potency of various nucleotides on membrane voltage and free cytosolic calcium concentration was UTP ≈ UDP > [adenosine 5′- O-(3-thiotriphosphate) (ATP-γ-S)] > ATP > 2-methylthioadenosine 5′-triphosphate (2-MeS-ATP) > 2′- and 3′- O-(4-benzoylbenzoyl)-adenosine 5′-triphosphate (BzATP) > ADP-β-S. α,β-Me-ATP was without effect. In the presence of UTP, BzATP did not cause an additional depolarization of podocytes. Incubation of cells with ATP or BzATP did not induce lactate dehydrogenase release. In RT-PCR studies, mRNAs of the P2Y1, P2Y2, P2Y6, and P2X7 receptors were detected within glomeruli and podocytes. The data indicate that extracellular nucleotides modulate podocyte function mainly by an activation of both P2Y2 and P2Y6 receptors.