Abstract
Testosterone synthesis within Leydig cells is a calcium-dependent process. Intracellular calcium levels are regulated by different processes including ATP-activated P2X purinergic receptors, T-type Ca2+ channels modulated by the luteinizing hormone, and intracellular calcium storages recruited by a calcium-induced calcium release mechanism. On the other hand, nitric oxide (NO) is reported to have an inhibitory role in testosterone production. Based on these observations, we investigated the interaction between the purinergic and nitrergic systems in Leydig cells of adult mice. For this purpose, we recorded ATP-evoked currents in isolated Leydig cells using the whole cell patch clamp technique after treatment with L-NAME (300 μM and 1 mM), L-arginine (10, 100, 300, and 500 μM), ODQ (300 μM), and 8-Br-cGMP (100 μM). Our results show that NO produced by Leydig cells in basal conditions is insufficient to change the ATP-evoked currents and that extra NO provided by adding 300 μM L-arginine positively modulates the current through a mechanism involving the NO/cGMP signaling pathway. Thus, we report an interaction between the nitrergic and purinergic systems in Leydig cells and suggest that Ca2+ entry via the purinergic receptors can be regulated by NO.
Highlights
The involvement of Ca2+ in Leydig cell’s testosterone synthesis was suggested by Janszen et al [1] by showing that the production of the hormone induced by the luteinizing hormone was dependent on the presence of Ca2+ in the extracellular solution
These results show that in our experimental conditions (ATP applied for 1400 ms + 5 min washout), the evoked purinergic currents suffered no significant desensitization
We demonstrated that purinergic and nitrergic systems interact in mice Leydig cells
Summary
The involvement of Ca2+ in Leydig cell’s testosterone synthesis was suggested by Janszen et al [1] by showing that the production of the hormone induced by the luteinizing hormone was dependent on the presence of Ca2+ in the extracellular solution. Other studies investigating the role of calcium ions in the steroidogenic process showed that application of ATP onto the cell increased the intracellular Ca2+ concentration [2] and the production of the steroid via activation of P2 receptors in Leydig cells [3]. Antonio et al [5,6] showed that P2X2, P2X4, P2X6, P2X7 subunits are present in Leydig cells, possibly arranged as heterotrimers to form P2X2/4/6 receptors. The increase in intracellular calcium concentration ([Ca2+]i) due to P2X receptor activation is one of the processes that can enhance steroidogenesis in Leydig cells. Several studies have shown an inverse relationship between NO and testosterone production/
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