FIGURE 5.

Hap1 deficiency decreases the Ca²⁺ influx. Fura-2 Ca²⁺ microfluorimetry of INS-1 cells transfected with Hap1-siRNA or scramble-siRNA plasmids. The cells were incubated in Fura-2 for 20 min prior to 30 mm K⁺ stimulation, which induced a transient increase of cytosolic Ca²⁺ concentration. A, representative trace of depolarization-induced increase in [Ca²⁺]_i in INS-1 cells expressing scramble-siRNA vector. B, depolarization-induced increase in [Ca²⁺]_i in INS-1 cells expressing Hap1-siRNA vector. C, averaged peak 340/380 intensity ratio recorded from INS-1 cells transfected with Hap1-siRNA or scramble-siRNA vector (**, p < 0.001; scramble n = 26, siRNA n = 26). D, Ca²⁺ entry through L-type Ca²⁺ channels was activated by a depolarizing stimulation of extracellular 30 mm K⁺, and the elevation level of intracellular Ca²⁺ was completely inhibited by 10 μm L-type Ca²⁺ channel blocker nifedipine.