Calcium-Activated Potassium Channels Expressed In Retinal Pigment Epithelial Cell

Retinal pigment epithelium (RPE) cell serves very important functions to support vision. The aim of this study was to identify which the expression of K Ca channels and ATP‐induced Ca 2+ transient lead to the activation of SK channels as well as those of BK channels in the ARPE‐19 cells. We used reverse transcription polymerase chain reaction and electrophysiological patch clamp recordings to investigate the expression and characteristics of 3 types of the K ca channel subunits, BK, IK and SK. The presence of Ca 2+ activated K + channels were identified by expression profile of transcripts encoding BK and SK channel subunits (i.e., BK α 1 , BK β 3 , BK β 4 , SK 1 , SK 3 and SK 4 /IK). 1‐ethyl‐2‐benzimidazolinone (EBIO), a specific SK channel activator, increased the whole‐cell current amplitude to 440.9% of control (at 50 mV, n = 8, p < 0.01), whereas apamin, a specific SK channel blockers, attenuated the outward currents by to 72.5% of control when BK and IK channels were blocked with iberiotoxin (IBTX) and clotrimazole (CLT) (at 50 mV, n = 6, p < 0.05). The single channel conductance of SK channel was 17.5 ± 0.8 pS in the symmetrical high K + solutions (145/145 mM, n = 6). ATP (100μM) increased the NP o of the channels in cell‐attached patch mode (from 0.11 ± 0.26 to 0.40 ± 0.10 at 0 mV, n = 6, p < 0.05). We suppose that SK channels related closely to these purinergic signals may play a role of important functions in the physiology of RPE cells.