ラット培養血管平滑筋細胞の電位依存性L型Ca²⁺チャネル電流はpp60^src過剰発現により増加する

抄録

Although angiotensin II (Ang II) has been reported to increase L-type Ca²⁺ channel current (I_Ca(L)) in vascular smooth muscle (VSM) cells, the mechanism how Ang II stimulates I_Ca(L) is not clarified. Since pp60^src is activated by Ang II, we investigated whether activation of pp60^src increases I_Ca(L) in cultured rat VSM cells (A7r5). A7r5 cells were transfected with a plasmid of wild type mouse src cDNA/pUSE expression vector using lipofectamine. Negative control cells were prepared by transfection with an empty vector, (-)/pUSE. After transfection, the cells were treated with 1 mg/ml of G418 to select the positive cells stably expressing src cDNA or (-)/pUSE. I_Ca(L) was recorded by whole-cell voltage clamp using a patch-clamp technique. 5 mM BaCl₂ was used as a charge carrier for recording of I_Ca(L). Western blot demonstrated that expression of pp60^src was increased by 34-fold in src cDNA/pUSE expressing cells as compared with (-)/pUSE expressing cells. Current/voltage relationships demonstrated that although voltages for peak amplitude of I_Ca(L) were 20 mV for both src cDNA and (-)/pUSE expressing cells, peak amplitude of I_Ca(L) in src cDNA/pUSE expressing cells was increased by 2-fold (src, 6.1±0.96; (-), 3.1±0.38 pA/pF). From steady-state inactivation and activation analyses of I_Ca(L), voltages for half-activation and -inactivation and slope factors did not differ between src and (-)/pUSE expressing cells. Thus, overexpression of pp60^src increases I_Ca(L) without affecting voltage sensors of L-type Ca²⁺ channels. [J Physiol Sci. 2007;57 Suppl:S235]