ISSN:
1432-2013
Keywords:
Rat hepatocytes
;
Electrophysiology
;
Membrane potentials
;
Na+ conductance
;
Bile acids
;
Taurocholic acid
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Rat hepatocytes in primary culture were impaled with conventional microelectrodes. Addition of 5–100 μmol/l taurocholate led to a slowly developing depolarization that was maximal at 50 μmol/l (10.5±1.5 mV, n=15) and not reversible. The effect was Na+ dependent and decreased in cells preincubated with 1 μmol/l taurocholate. Increasing external K+ tenfold depolarized the cells by 12.3±2.3 mV under control conditions and by 6.3±1.2 mV with 50 μmol/l taurocholate present (n=7). Depolarization by 1 mmol/l Ba2+ was 7.6±0.8 mV and 6.0±0.7 mV (n=9) before and after addition of taurocholate, respectively. Cable analysis and Na+ substitution experiments reveal that this apparent decrease in K+ conductance reflects an actual increase in Na+ conductance: in the presence of taurocholate, specific cell membrane resistance decreased from 2.8 to 2.3 kΩ · cm2 · Na+ substitution by 95% depolarized cell membranes by 8.9±2.9 mV (n=9), probably due to indirect effects on K+ conductance via changes in cell pH. With taurocholate present, the same manoeuvre changed membrane voltages by −0.8±2.6 mV. When Na+ concentration was restored to 100% from solutions containing 5% Na+, cells hyperpolarized by 3.5±3.6 mV (n=7) under control conditions and depolarized by 4.4±2.9 mV in the presence of taurocholate, respectively. In Cl− substitution experiments, there was no evidence for changes in Cl− conductance by taurocholate. These results show that taurocholate-induced membrane depolarization is due to an increase in Na+ conductance probably via uptake of the bile acid.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00374605
