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Pharmacological properties of the T-type Ca2+ current of mouse spermatogenic cells
C Arnoult1, M Villaz, H M Florman
1Laboratoire de Biophysique Moléculaire et Cellulaire, CNRS URA 520, CEA/Grenoble, 38054 Grenoble, France. arnoult@dsvgre.cea.fr
Abstract:
The effects of pharmacological agents on the T-type Ca2+ current were studied in dissociated spermatogenic cells from the mouse. Ca2+ currents were elicited by depolarization in 10 mM Ca2+ and recorded in the whole-cell configuration of the patch clamp technique. The T-type current was inhibited by the following compounds: PN200-110 (IC50 = 4 x 10(-8) M) > nifedipine (IC50 = 4 x 10(-7) M) > pimozide (IC50 = 4.6 x 10(-7) M) > mibefradil (IC50 = 5 x 10(-6) M) > Ni2+ (IC50 = 3.4 x 10(-5) M) > verapamil (IC50 = 7 x 10(-5) M) > amiloride (IC50 = 2.4 x 10(-4) M) > Cd2+ (IC50 = 2.8 x 10(-4) M). However, the agents differed in the reversibility and the use dependence of their effects. Currents recovered rapidly and completely after removal of Ni2+, Cd2+, amiloride, or mibefradil, whereas recovery from verapamil block was rapid but incomplete. In contrast, we observed little recovery after the removal of pimozide and of the dihydropyridines (PN200-110, nifedipine). Moreover, mibefradil and pimozide exhibit a strongly use-dependent inhibition of current that is due to selective interaction of these drugs with the open state and the inactivated state of the channel, respectively, rather than with the resting state. These properties of the spermatogenic T-type Ca2+ channel differ from those of somatic cell T channels and suggest a molecular diversity of low voltage-activated Ca2+ channels.
Insights
Pharmacological agents differentially affect T-type calcium channels in mouse spermatogenic cells. These T-type calcium channels exhibit unique properties distinct from somatic cells, suggesting molecular diversity.
Area of Science:
- Pharmacology
- Cell Biology
- Reproductive Biology
Background:
- T-type calcium channels are crucial for cellular functions.
- Understanding their role in spermatogenesis is important for reproductive health.
- Pharmacological modulation provides insights into channel function.
Purpose of the Study:
- To investigate the effects of various pharmacological agents on T-type calcium current in mouse spermatogenic cells.
- To characterize the inhibition, reversibility, and use-dependence of these agents.
- To compare the properties of spermatogenic T-type calcium channels with those in somatic cells.
Main Methods:
- Dissociated mouse spermatogenic cells were used.
- Patch clamp technique in whole-cell configuration was employed.
- Calcium currents were elicited by depolarization in 10 mM Ca2+.
Main Results:
- Several agents inhibited T-type current, with varying IC50 values (e.g., PN200-110, nifedipine, pimozide).
- Inhibition reversibility differed significantly among agents.
- Mibefradil and pimozide showed use-dependent inhibition, interacting with open and inactivated channel states.
Conclusions:
- Spermatogenic T-type calcium channels possess distinct pharmacological properties compared to somatic T-type channels.
- These differences suggest molecular diversity among low voltage-activated calcium channels.
- This finding has implications for understanding calcium signaling in male reproduction.