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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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