Journal of Nippon Medical School: Vol.66 No.2 page.127

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ArticleTitle Evidence for norepinephrine-activated Ca²⁺ permeable channels in guinea-pig hepatocytes using a patch clamp technique

AuthorList Tomoo Nagano¹⁾, Ryoichi Sato²⁾, Hiroyuki Matsuda¹⁾ and Takumi Aramaki¹⁾

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 November 18, 1998

Accepted January 11, 19 99

Keywords patch clamp technique, guinea-pig hepatocyte, Ca²⁺ channel, norepinephrine

Abstract To determine whether the hepatocyte plasma membrane possesses a Ca²⁺ channel, we applied a patch clamp technique to isolated guinea-pig hepatocytes. In a cell-attached configuration, using an internal pipette solution of 110mM BaCl₂ or CaCl₂, 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 Ca²⁺ 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 Ca²⁺ permeable channels that differ from the voltage-operated Ca²⁺ channels found in excitable cells and that such channels are responsible for the agonist-stimulated Ca²⁺ 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

ArticleTitle	Evidence for norepinephrine-activated Ca²⁺ permeable channels in guinea-pig hepatocytes using a patch clamp technique
AuthorList	Tomoo Nagano¹⁾, Ryoichi Sato²⁾, Hiroyuki Matsuda¹⁾ and Takumi Aramaki¹⁾
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	November 18, 1998
Accepted	January 11, 19 99
Keywords	patch clamp technique, guinea-pig hepatocyte, Ca²⁺ channel, norepinephrine
Abstract	To determine whether the hepatocyte plasma membrane possesses a Ca²⁺ channel, we applied a patch clamp technique to isolated guinea-pig hepatocytes. In a cell-attached configuration, using an internal pipette solution of 110mM BaCl₂ or CaCl₂, 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 Ca²⁺ 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 Ca²⁺ permeable channels that differ from the voltage-operated Ca²⁺ channels found in excitable cells and that such channels are responsible for the agonist-stimulated Ca²⁺ 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