In recent years, a large amount of studies is dedicated to understand the role of ATP as an intercellular signaling agent. Several evidences confirm its function as a mediator and/or modulator of both fast events, like the neurotransmission, as well as of long term cellular processes, involving G proteins. ATP acts on the plasma membrane by interacting with purinergic receptors P2X (ligand-gated ion channels) and P2Y (G protein-coupled receptors). Until now, seven subunits of P2X receptors were identified and cloned (P2X1 - P2X7), which form trimeric arrangements in functional receptors. Homomeric receptors P2X1-7 and heteromeric receptors P2X1/2, P2X1/4, P2X1/5, P2X2/3, P2X2/6, P2X4/6 e P2X4/7 have distinct biophysical and pharmacological properties. Calcium influx through these channels is in part responsible for the increase in intracellular [Ca2+] observed in a number of physiological situations, indicating an important role for P2X receptors "in vivo". ATP treatment of Leydig cells from mice and rats, leads to an increase in [Ca2+]i and testosterone secretion, supporting the hypothesis that Ca2+ signaling contributes to the process of testosterone secretion in these cells. Purinergic receptors subunits P2X2, P2X4, P2X6 and P2X7 are present in Leydig cells, but receptors P2X7 and P2X4/7 are not functional. Furthermore, evidences indicate that functional receptors are heteromers P2X2/4/6, which exhibit a pharmacological profile typical of the dominant P2X2 subunit. In this work we aimed at investigating the possible interactions between P2X purinergic receptors subunits present in mouse Leydig cells by analyzing their molecular and electrophysiological properties.
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