Two Types of Calcium Channels in Human Ovarian Endocrine Cells: Involvement in Steroidogenesis

Abstract

Nature, regulation, and functional role of ion channels of human ovarian endocrine cells are not well known. In our present study, we show two types of voltage-activated Ca(2+) currents (I(Ca)) in cultured human luteinized granulosa cells (GCs), as assessed by whole-cell patch-clamp experiments. Electrophysiological properties, namely low threshold of activation, pronounced time-dependent inactivation, slow and voltage-dependent deactivation kinetics, insensitivity to SNX-482, and high sensitivity to Ni(2+), defined the predominant I(Ca) as a T-type Ca(2+) current (I(Ca.T)). In 4% of cells a Ni(2+)-insensitive I(Ca) was measured alone or together with I(Ca.T). This Ca(2+) current was high voltage activated and highly sensitive to dihydropyridine, indicative of an L-type Ca(2+) current. RT-PCR analysis demonstrated the presence of mRNA coding for alpha(1)-subunits of two different Ca(2+) channels (T-type Ca(v)3.2 and L-type Ca(v)1.2) in GCs. In addition, these two types were detected in the human corpus luteum by RT-PCR (Ca(v)3.2) and immunohistochemistry (Ca(v)1.2). Although stimulation of cultured GCs with human chorionic gonadotropin did not change the characteristics of recorded I(Ca.T), it markedly increased the percentage of cells displaying I(Ca) from 29 to 63% and significantly increased (2.2-fold) the density of I(Ca.T). Furthermore, the stimulatory effect of human chorionic gonadotropin on progesterone production was diminished by pharmacological blockage of I(Ca.T) by Ni(2+) or flunarizine. Thus, our study provides evidence that human GCs in vivo and in vitro express T- and L-type Ca(2+) channels and that the Ca(v)3.2 (also called alpha(1H)) isoform is involved in a fundamental endocrine function of these cells.

Perillyl Alcohol Inhibits a Calcium-Dependent Constitutive Nuclear Factor-κB Pathway

“…The sequence of the primers and conditions used to amplify the LTCC gene from human breast cancer lines have been published (23,24). The sequencing of the resulting PCR products was as described above.…”

Mechanisms of Intracellular Calcium Homeostasis in Developing and Mature Bovine Corpora Lutea1

“…Pharmacological studies demonstrated that transport of Ca 2þ via VGCCs participated in the luteinization process of porcine granulosal cells [59]. Expression and functional evidence of VGCCs in human CL (unknown luteal phase) and human luteinized granulosal cells have been reported, with both L and T types expressed and shown to be involved in steroidogenesis [35]. The difference in the type of these channels expressed in the human and cow may be species related.…”

“…The contribution of the extracellular milieu in increasing [Ca 2þ ] i is mediated by members of the voltage-gated calcium channel (VGCC) family: L, N and T types [28,32]. Land T-type VGCCs were found in several types of steroidogenic cells, such as bovine adrenal glomerulosal cells, [33], mouse Leydig cells [34], and human granulosal cells [35].…”

Voltage‐dependent K+ channel acts as sex steroid sensor in endocrine cells of the human ovary

“…Scale bars, 200 mm (A, B), 50 mm (C, D), 100 mm (E-H). (Agoston et al, 2004), the peak voltage of the I A window current was far too negative for being of relevance under physiological conditions. K v 4.2 channels were not functional in our study in the first days of culture despite the abundance of a prominent I A and the presence of K v 4.2 mRNA already on the first day (not shown).…”

“…Recently, we have identified a Ca 2þ -activated large conductance K þ channel (BK Ca ) (Kunz et al, 2002), voltage-activated Ca 2þ channels (Agoston et al, 2004), and an endocrine Na þ channel in human GCs (Bulling et al, 2000). Furthermore, a transient A-type like K þ current (I A ) was earlier shown to be abundant in human GCs (Bulling et al, 2000).…”