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C.–N. Liu, C. Somps; Voltage–Dependent Potassium Currents in the B – 3 Human Lens Eepithelial Cell Line . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1858.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: K+ conductance plays an important role in maintaining ionic function in lens epithelial cells. Our previous work showed that an outwardly–rectified, TEA– sensitive current is extensively expressed in the SRA 01/04 human lens epithelial cell line and likely participates in the regulatory volume control of these cells. The aim of the current work was to characterize the electrophysiological properties of B – 3 cells, another human lens epithelial cell line. Methods: Human lens B – 3 cells were cultured in EMEM (with 20% serum, ATCC) at 37° C and 95% O2 and 5% CO2. The whole–cell patch–clamp configuration was used to study trans–membrane currents. Membrane potential was held at –60 mV and square pulses of 250 ms duration were applied in 20 mV steps between –120 mV and +140 mV. Additionally, resting membrane potentials were measured under current–clamp mode. Tetraethylammonium (TEA) and iberiotoxin (IbTx) were pipetted directly into the bath at 25°C to pharmacologically evaluate trans–membrane currents. Results: Tested cells ranged in diameter between 17 – 23 µm. The depolarizing pulse stimulation evoked an outward current starting at + 40 – + 50mV in 31% of the cells tested (16/52). The mean value of these currents was 1818 ± 456 pA (means ± SE ) at +140 mV. In a majority of these cells (14/16), elicited currents do not show inactivation over the 250 ms depolarization. Currents were diminished within minutes by extracellular application of 100 µM to 25 mM TEA, with an IC 50 = 0.34 ± 0.02 mM (n = 5). 100 nM IbTx inhibited outward currents by 59 ± 6 % (n = 4). There were no significant differences in the resting potential (–23.4 ± 14.7 vs. – 30.6 ± 5.2 mV) and membrane capacitance ( 19.7 ± 2.0 vs. 17.0 ± 1.4 pF) between cells with the potassium currents and those without (P > 0.05). Conclusions: B – 3 cells express a TEA–sensitive, outwardly–rectified current with electrophysiologic and pharmacolgic characteristics similar to those observed previously in the SRA lens epithelial cell line. However, its prevalence is only 31 % in B – 3 cells compared to nearly 100% in the SRAs.
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