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

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 Ca2+ currents (ICa) 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 Ni2+, defined the predominant ICa as a T-type Ca2+ current (ICa.T). In 4% of cells a Ni2+-insensitive ICa was measured alone or together with ICa.T. This Ca2+ current was high voltage activated and highly sensitive to dihydropyridine, indicative of an L-type Ca2+ current. RT-PCR analysis demonstrated the presence of mRNA coding for α1-subunits of two different Ca2+ channels (T-type Cav3.2 and L-type Cav1.2) in GCs. In addition, these two types were detected in the human corpus luteum by RT-PCR (Cav3.2) and immuno...