Mouse Leydig cells express multiple P2X receptor subunits

ATP acts on cellular membranes by interacting with P2X (ionotropic) and P2Y (metabotropic) receptors. Seven homomeric P2X receptors (P2X 1 –P2X 7 ) and seven heteromeric receptors (P2X 1/2 , P2X 1/4 , P2X 1/5 , P2X 2/3 , P2X 2/6 , P2X 4/6 , P2X 4/7 ) have been described. ATP treatment of Leydig cells leads to an increase in [Ca 2+ ] i and testosterone secretion, supporting the hypothesis that Ca 2+ signaling through purinergic receptors contributes to the process of testosterone secretion in these cells. Mouse Leydig cells have P2X receptors with a pharmacological and biophysical profile resembling P2X 2 . In this work, we describe the presence of several P2X receptor subunits in mouse Leydig cells. Western blot experiments showed the presence of P2X 2 , P2X 4 , P2X 6 , and P2X 7 subunits. These results were confirmed by immunofluorescence. Functional results support the hypothesis that heteromeric receptors are present in these cells since 0.5 μM ivermectin induced an increase (131.2 ± 5.9%) and 3 μM ivermectin a decrease (64.2 ± 4.8%) in the whole-cell currents evoked by ATP. These results indicate the presence of functional P2X 4 subunits. P2X 7 receptors were also present, but they were non-functional under the present conditions because dye uptake experiments with Lucifer yellow and ethidium bromide were negative. We conclude that a heteromeric channel, possibly P2X 2/4/6 , is present in Leydig cells, but with an electrophysiological and pharmacological phenotype characteristic of the P2X 2 subunit.