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Published on: January 10, 2011
Evidence for norepinephrine-activated Ca2+ permeable channels in guinea-pig hepatocytes using a patch clamp technique
1First Department of Internal Medicine, Nippon Medical School, Tokyo, Japan.
Nihon Ika Daigaku Zasshi
|May 26, 1999
Summary
Hepatocytes possess calcium (Ca2+) channels distinct from those in excitable cells. These channels facilitate agonist-stimulated Ca2+ entry, crucial for liver cell function.
Area of Science:
- Cell Biology
- Physiology
- Ion Channel Research
Background:
- Hepatocytes are vital liver cells involved in numerous metabolic functions.
- Understanding calcium (Ca2+) signaling in hepatocytes is crucial for comprehending liver physiology and disease.
- The presence and nature of Ca2+ channels in the hepatocyte plasma membrane remain incompletely characterized.
Purpose of the Study:
- To investigate the existence and properties of Ca2+ channels in the plasma membrane of guinea-pig hepatocytes.
- To characterize the functional behavior of these putative Ca2+ channels using electrophysiological techniques.
- To determine if these channels are distinct from known voltage-operated Ca2+ channels and contribute to agonist-induced Ca2+ influx.
Main Methods:
- Patch clamp technique applied to isolated guinea-pig hepatocytes in a cell-attached configuration.
- Utilized BaCl2 or CaCl2 as charge carriers in the internal pipette solution.
- Recorded single channel currents at various membrane potentials and analyzed channel properties (conductance, open probability, voltage dependence).
Main Results:
- Observed sporadic inward single channel currents indicative of Ca2+ permeability.
- Determined a single channel conductance of 20.4 +/- 4.6 pS, with no rectification or voltage dependence.
- Found that Bay K 8644 (a dihydropyridine Ca2+ channel activator) did not affect channel activity, while external norepinephrine increased it.
Conclusions:
- Guinea-pig hepatocytes possess Ca2+ permeable channels.
- These channels differ significantly from voltage-operated Ca2+ channels found in excitable cells.
- The identified channels are likely responsible for agonist-stimulated Ca2+ entry in hepatocytes, playing a key role in liver cell signaling.
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