Inhibitory actions of mibefradil on steroidogenesis in mouse Leydig cells: involvement of Ca2+ entry via the T-type Ca2+ channel

Abstract

Intracellular cAMP and Ca 2+ are involved in the regulation of steroidogenic activity in Leydig cells, which coordinate responses to luteinizing hormone (LH) and human chorionic gonadotropin (hCG). However, the identification of Ca 2+ entry implicated in Leydig cell steroidogenesis is not well defined. The objective of this study was to identify the type of Ca 2+ channel that affects Leydig cell steroidogenesis. In vitro steroidogenesis in the freshly dissociated Leydig cells of mice was induced by hCG incubation. The effects of mibefradil (a putative T-type Ca 2+ channel blocker) on steroidogenesis were assessed using reverse transcription (RT)-polymerase chain reaction analysis for the steroidogenic acute regulatory protein (StAR) mRNA expression and testosterone production using radioimmunoassay. In the presence of 1.0 mmol L −1 extracellular Ca 2+ , hCG at 1 to 100 IU noticeably elevated both StAR mRNA level and testosterone secretion (P < 0.05), and the stimulatory effects of hCG were markedly diminished by mibefradil in a dose-dependent manner (P < 0.05). Moreover, the hCG-induced increase in testosterone production was completely removed when external Ca 2+ was omitted, implying that Ca 2+ entry is needed for hCG-induced steroidogenesis. Furthermore, a patch-clamp study revealed the presence of mibefradil-sensitive Ca 2+ currents seen at a concentration range that nearly paralleled those inhibiting steroidogenesis. Collectively, our data provide evidence that hCG-stimulated steroidogenesis is mediated at least in part by Ca 2+ entry carried out by the T-type Ca 2+ channel in the Leydig cells of mice.

Nifedipineon;

“…En masse, these results depicted that Ca 2+ entry is required for steroidogenesis in Leydig cells. 25 These findings are in parallel with our results.…”

Calcium Signaling in Interstitial Cells: Focus on Telocytes

“…To date, the luteinizing hormone was shown to modulate the T-type calcium channels and the intracellular Ca 2+ transients through PKC and PKA signaling pathways, and thus, these kinases, besides the direct action to promote testosterone synthesis, also act on the overall calcium dynamics in Leydig cells [ 103 ]. Mibefradil was shown to inhibit T-type calcium channels in Leydig cells and steroidogenesis is linked to the Ca 2+ entry through the T-type Ca 2+ channel [ 104 ].…”

Gonadotropin-releasing hormone positively regulates steroidogenesis via extracellular signal-regulated kinase in rat Leydig cells

“…MA-10 Leydig tumour cells have been used extensively to study many of the functions of Leydig cells. [25][26][27][28] . However, the primary culture system employed in this study more closely resembles the cells in vivo.…”