Changes in inward rectifier K⁺ channels in hepatic stellate cells during primary culture

Purpose: This study examined the expression and function of inward rectifier K⁺ channels in cultured rat hepatic stellate cells (HSC). Materials and Methods: The expression of inward rectifier K^- channels was measured using real-time RT-PCR, and electrophysiological properties were determined using the gramicidin-perforated patch-clamp technique. Results: The dominant inward rectifier K⁺ channel subtypes were K_ir2.1 and K_ir6.1. These dominant K⁺ channel subtypes decreased significantly during the primary culture throughout activation process. HSC can be classified into two subgroups: one with an inward-rectifying K⁺ current (type 1) and the other without (type 2). The inward current was blocked by Ba²⁺ (100 μM) and enhanced by high K^- (140 mM), more prominently in type 1 HSC. There was a correlation between the amplitude of the Ba^2--sensitive current and the membrane potential. In addition, Ba²⁺ (300 μM) depolarized the membrane potential. After the culture period, the amplitude of the inward current decreased and the membrane potential became depolarized. Conclusion: HSC express inward rectifier K⁺ channels, which physiologically regulate membrane potential and decrease during the activation process. These results will potentially help determine properties of the inward rectifier K⁺ channels in HSC as well as their roles in the activation process.