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ArticleTitle | Evidence for norepinephrine-activated Ca 2+ permeable channels in guinea-pig hepatocytes using a patch clamp technique |
AuthorList | Tomoo Nagano 1) , Ryoichi Sato 2) , Hiroyuki Matsuda 1) and Takumi Aramaki 1) |
Affiliation | 1) First Department of Internal Medicine, Nippon Medical School, and 2) Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School |
Language | EN |
Volume | 66 |
Issue | 2 |
Year | 1999 |
Page | 127-133 |
Received | Novembe r 18, 1998 |
Accepted | January 11, 1999 |
Keywords | patch clamp technique, guinea-pig hepatocyte, Ca 2+ channel, norepinephrine |
Abstract | To determine whether the hepatocyte plasma membrane possesses a Ca 2+ channel, we applied a patch clamp technique to isolated guinea-pig hepatocytes. In a cell-attached configuration, using an internal pipette solution of 110mM BaCl 2 or CaCl 2 , we observed sporadic inward single channel currents (Po=0.004± 0.002, n=6) at various membrane potentials. The unit amplitude was 0.60± 0.15pA (n=6) at resting membrane potential. The single channel conductance was 20.4± 4.6 pS (n=6) and this channel showed no rectification and no voltage dependence. Bay K 8644, a dihydropyridine Ca 2+ channel activator, did not affect this channel activity. Although norepinephrine in the pipette solution did not activate this channel, its external application increased channel activity. These observations suggest that guinea-pig hepatocytes possess Ca 2+ permeable channels that differ from the voltage-operated Ca 2+ channels found in excitable cells and that such channels are responsible for the agonist-stimulated Ca 2+ entry in hepatocytes. |
Correspondence to | Tomoo Nagano, First Department of Internal Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan |
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