Figure 4. Effect of hBest1 and hBest1^W93C expression on Ca²⁺-stimulated changes in transepithelial electrical properties. A: fhRPE cells were treated with 500 nM ionomycin, which caused a biphasic increase in TEP. Each phase of the response was measured at the indicated point. When the TEP reached a plateau, 100 µM NFA was added to the bathing solution to inhibit calcium-activated anion channel activity. Representative recordings of responses are shown in (B), demonstrating that overexpression of either hBest1 or hBest1^W93C resulted in a suppression of the overall response, and that the response to the addition of NFA was similar in control and monolayers overexpressing hBest1. I_sc (C) was determined from TEP (D) and TER (E) for P0, P1, P2, and NFA. Responses were elevated at P0 for hBest1-overexpressing monolayers compared to controls and monolayers overexpressing hBest1^W93C. However, at P1, P2, and NFA, I_sc was not significantly different between controls and monolayers overexpressing hBest1. Neither ionomycin nor NFA had a significant effect on the transepithelial electrical properties of fhRPE monolayers expressing hBest1^W93C. Compared to control and hBest1-overexpressing monolayers, TEP (D) and I_sc (C) were significantly reduced for hBest1^W93C monolayers at P0, P1, P2, and NFA. For both control and hBest1-overexpressing monolayers, the differences in TEP (D) and I_sc (C) between different time points were significant (p<0.05). Data are mean ± SD, n=9 for control, n=5 for hBest1, and n=6 for W93C.