Characteristics of potassium and calcium currents of hepatic stellate cells (Ito) in rat

Hepatic stellate cells (HSCs) are known to play a role in the pathogenesis of the increased intrahepatic vascular resistance found in chronic liver diseases. The aim of this study was to evaluate the K⁺ and Ca²⁺ currents in cultured HSCs from rat liver, through the patch-clamp technique. Most cells were positive for desmin immunostain after isolation and in α-smooth muscle actin immunostain after 10 - 14 days of culturing. Outward and inward rectifying K⁺ currents were confirmed. Two different types of K⁺ currents were distinguished: one with the inward rectifying current and the other without. The outward K⁺ currents consisted of at least four components: tetraethylammonium (TEA -sensitive current, 4-aminopyridine (4-AP)-sensitive current, pimozide-sensitive current and three blocker-resistant current. The peaks of the outward K⁺ currents evoked by a depolarizing pulse were decreased to 32.0 ± 3.0, 62.8 ± 3.7 and 32.8 ± 3.5% by 5 mM TEA, 2 mM 4-AP and 15 μM pimozide, respectively. Moreover, the combined application of three blockers caused 86.6 ± 4.8% suppression. The inward currents evoked hyperpolarizing pulses were inwardly rectifying and almost blocked by Ba²⁺. Elevation of external K⁺ increased the inward current amplitude and positively shifted its reversal potential. Voltage-dependent Ca²⁺ currents which were completely abolished by Cd²⁺ and nimodipine were detected in 14 day cultured HSCs. In this study, the cultured HSCs were found to express outward K⁺ current composed of multiple pharmacological components, Ba²⁺-sensitive inward rectifying K⁺ current and L-type Ca²⁺ current.