Welling A, Felbel J, Peper K, Hofmann F
Physiologisches Institut, Medizinische Fakultät, Universität des Saarlandes, Homburg/Saar, Federal Republic of Germany.
Am J Physiol. 1992 Mar;262(3 Pt 1):L351-9. doi: 10.1152/ajplung.1992.262.3.L351.
Single freshly isolated smooth muscle cells of adult bovine trachea were voltage clamped, and the calcium inward current was separated from K+ currents by blocking the large outward currents with intra- and extracellular Cs+ and extracellular tetraethylammonium chloride. Isoproterenol stimulated peak calcium current (ICa) in a dose-dependent manner through the beta-adrenergic receptor. The isoproterenol effect was not mediated or caused by the stimulation of a K+ or Na+ current, a decrease in the intracellular concentrations of Ca2+ or H+, the stimulation of the Na(+)-H+ or the Na(+)-Ca2+ exchanger. Neither basal nor isoproterenol-stimulated ICa was affected by internal dialysis of the cell with adenosine 3',5'-cyclic monophosphate (cAMP), cAMP analogues, or the catalytic subunit of cAMP-kinase. Internal dialysis of the cells with guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) blocked the stimulation of isoproterenol whereas dialysis with guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) induced an isoproterenol-like maximal increase of ICa. These results show that the beta-adrenergic receptor stimulates the L-type calcium current of isolated tracheal smooth muscle cells independent of cAMP and cAMP-kinase through a GTP/GDP regulated protein.
对成年牛气管新鲜分离的单个平滑肌细胞进行电压钳制，通过细胞内和细胞外的铯离子（Cs+）以及细胞外的四乙铵氯化物阻断大的外向电流，从而将钙内向电流与钾离子电流分离。异丙肾上腺素通过β-肾上腺素能受体以剂量依赖的方式刺激钙电流峰值（ICa）。异丙肾上腺素的作用不是由钾离子或钠离子电流的刺激、细胞内钙离子或氢离子浓度的降低、钠氢交换体（Na(+)-H+）或钠钙交换体（Na(+)-Ca2+）的刺激介导或引起的。用3',5'-环磷酸腺苷（cAMP）、cAMP类似物或cAMP激酶的催化亚基对细胞进行内部透析，对基础ICa或异丙肾上腺素刺激的ICa均无影响。用5'-O-(2-硫代二磷酸)鸟苷（GDPβS）对细胞进行内部透析可阻断异丙肾上腺素的刺激作用，而用5'-O-(3-硫代三磷酸)鸟苷（GTPγS）进行透析则可诱导出类似异丙肾上腺素的ICa最大增加。这些结果表明，β-肾上腺素能受体通过一种GTP/GDP调节蛋白，独立于cAMP和cAMP激酶刺激分离的气管平滑肌细胞的L型钙电流。
