The Effect of Mibefradil on Calcium Currents in Primary Human Lens Epithelial Cells
Beck R.1, Kunz F.2, Nebe B.2, Rychly J.2, Noack T.3
1Department of Ophthalmology, Rostock University, 2Clinic for Internal Medicine, Department for Clinical Research, 3Institute for Physiology, Rostock University
Purpose: Mibefradil, a T-type calcium channel blocker induces apoptosis and loss of cell adhesion in human lens epithelial cell culture. The membrane properties and Mibefradil induced changes which may lead to apoptosis were investigated using the whole-cell patch-clamp technique.
Method: Primary cultures of human lens epithelial cells (hLEC) were established from human anterior capsules obtained during cataract surgery. HLEC were dispersed by enzymatic treatment. Using patch-clamp, whole-cell currents were measured.
Results: Ion currents were composed of a rapid inward and slow outward current component. The outward current could be inhibited by intracellular application of caesium ions. The extracellular calcium concentration was 2,5 mM. Under these conditions inward calcium currents were recorded. The inward currents activated at potentials positive to -50 mV. The activation and inactivation kinetics were very fast and the total current was inactivated after 5 to 10 ms after the depolarizing pulse. Mibefradil 1 to 10 µM reduced the voltage-dependent inward calcium current, with an IC 50 close to 3 µM. When the cells were depolarized from three different holding p
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