Follicle-stimulating hormone-induced Gαh/phospholipase C-δ1 signaling mediating a noncapacitative Ca²⁺ influx through T-type Ca²⁺ channels in rat sertoli cells

Our previous study demonstrated that FSH-induced immediate Ca²⁺ influx in rat Sertoli cells (SCs) is mediated by the Gαh/phospholipase C-δ1 (PLC-δ1) signaling pathway. As to which Ca²⁺ channel is responsible for such Ca²⁺ influx was not understood. In this study, thapsigargin triggered an instore calcium release and evoked a 1.5-fold elevation of intracellular Ca²⁺ in Ca²⁺-free media, whereas FSH exhibited no effect. The readdition of CaCl₂ (2.5 mM) to FSH-pretreated or thapsigargin-sensitized SCs in Ca²⁺-free media immediately elicited a rapid Ca²⁺ influx or a 2-fold increase of second intracellular Ca²⁺ elevation, respectively. The addition of Ca²⁺ chelator EGTA (0.2 mM) reduced the FSH-induced elevation of intracellular Ca²⁺ in SCs incubated with CaCl₂. However, pretreatment with dantrolene (25 μM), which inhibits in-store calcium release, did not affect the FSH-induced elevation of intracellular Ca ²⁺. NiCl₂ (10 μM), a T-type calcium channel blocker, abolished the FSH-induced SC Ca²⁺ influx. Furthermore, mibefradil (10 and 100 μM), another specific blocker for T-type Ca²⁺ channels, dose-dependently suppressed the FSH-induced Ca²⁺ influx. In contrast, nifedipine (10 and 50 μM) or ω-conotoxin GVIA (100 and 500 nM), blocker of L- or N-type Ca²⁺ channels, respectively, did not affect the FSH-induced SC Ca²⁺ influx. On the other hand, FSH-induced Ca²⁺ influx was significantly reduced by pretreatment of SCs with myristoylated synthetic peptide (0.1 and 1 μM) of PLC-δ1 fragment TIPWNSLKQGYRHVHLL but not affected by 2′,5′-dideoxyadenosine (3 and 15 μM), a selective inhibitor of adenylate cyclase. In conclusion, the FSH-induced Gαh/PLC-δ1 pathway-dependent Ca²⁺ influx of rat SCs is mediated by T-type Ca²⁺ channels and independent of in-store calcium release.