Heterogeneous Composition of Voltage-Dependent K+ Currents in Hepatic Stellate Cells

PURPOSE: Hepatic stellate cells (HSC) are a type of pericyte with varying characteristics according to their location. However, the electrophysiological properties of HSC are not completely understood. Therefore, this study investigated the difference in the voltage-dependent K(+) currents in HSC. MATERIALS AND METHODS: The voltage-dependent K(+) currents in rat HSC were evaluated using the whole cell configuration of the patch-clamp technique. RESULTS: Four different types of voltage-dependent K(+) currents in HSC were identified based on the outward and inward K(+) currents. Type D had the dominant delayed rectifier K(+) current, and type A had the dominant transient outward K(+) current. Type I had an inwardly rectifying K(+) current, whereas the non-type I did not. TEA (5mM) and 4-AP (2mM) suppressed the outward K(+) currents differentially in type D and A. Changing the holding potential from -80 to -40mV reduced the amplitude of the transient outward K(+) currents in type A. The inwardly rectifying K(+) currents either declined markedly or were sustained in type I during the hyperpolarizing step pulses from -120 to -150mV. CONCLUSION: There are four different configurations of voltage-dependent K(+) currents expressed in cultured HSC. These results are expected to provide information that will help determine the properties of the K(+) currents in HSC as well as the different type HSC populations.

Effects of Tamoxifen on the Voltage-dependent Ionic Currents in Mouse Colonic Smooth Muscle Cells / 대한소화기학회지

BACKGROUND/AIMS: Tamoxifen is a widely used anticancer drug for breast cancer with frequent gastrointestinal side effects. Changes in gastrointestinal motility is associated with altered activities of membrane ion channels. Ion channels have important role in regulating membrane potential and cell excitability. This study was performed to investigate the effects of tamoxifen on the membrane ionic currents in colonic smooth muscle cells. METHODS: Murine colonic smooth muscle cells were isolated from the proximal colon using collagenase, and the membrane currents were recorded using a whole-cell patch clamp technique. RESULTS: Two types of voltage-dependent K+ currents were recorded (A-type and delayed rectifier K+ currents). Tamoxifen inhibited both types of voltage-dependent K+ currents in a dose-dependent manner. However, tamoxifen did not change the half-inactivation potential and the recovery time of voltage-dependent K+ currents. Chelerythrine, a protein kinase C inhibitor or phorbol 12, 13-dibutyrate, a protein kinase C activator did not affect the voltage-dependent K+ currents. Guanosine 5'-O-(2-thio-diphosphate) did not affect the tamoxifen-induced inhibition of voltage-dependent K+ currents. Tamoxifen inhibited voltage-dependent Ca2+ currents completely in whole-test ranges. CONCLUSIONS: These results suggest that tamoxifen can alter various membrane ionic currents in smooth muscle cells and cause some adverse effects on the gastrointestinal motility.