Kamimura N, Suga S, Wada J, Mio Y, Suzuki T, Wakui M
Department of Physiology, Hirosaki University School of Medicine, Japan.
J Cell Physiol. 1996 Nov;169(2):373-9. doi: 10.1002/(SICI)1097-4652(199611)169:2<373::AID-JCP17>3.0.CO;2-A.
The effect of norepinephrine (NE) was examined on the whole-cell Ba2+ current through L-type Ca2+ channels of freshly isolated smooth muscle cells of guinea-pig vas deferens. The magnitude of maximum Ba2+ current [1Ba(max)] varied in different cells, although the capacitance of the cell membrane was similar (approximately 50 pF). Application of dbcAMP augmented 1Ba(max) by 37%, which was canceled by Rp-cAMPs, while PMA decreased the current by 32%, which was canceled by staurosporine. NE increased 1Ba(max) of the cells which originally showed relatively small 1Ba(max), and decreased the current of the cells which showed larger 1Ba(max). In the presence of phentolamine, NE increased 1Ba(max), and this effect was remarkable in cells showed smaller 1Ba(max). In the presence of propranolol, NE decreased 1Ba(max). The excitatory beta-adrenoceptor activation was canceled by Rp-cAMPs, and the inhibitory alpha-adrenoceptor effect was canceled by staurosporine. It is suggested that NE shows dual (excitatory and inhibitory) actions on the L-type Ca2+ channels of smooth muscle of guinea-pig vas deferens. The excitatory beta-adrenoceptor action mediated through cAMP/PKA is predominant in cells with lower density of the Ca2+ channels, while inhibitory alpha-adrenoceptor action mediated through PKC is predominant in cells with higher channel density.
研究了去甲肾上腺素（NE）对豚鼠输精管新鲜分离平滑肌细胞L型钙通道全细胞Ba2+电流的影响。尽管细胞膜电容相似（约50 pF），但不同细胞中最大Ba2+电流[I Ba(max)]的大小有所不同。应用二丁酰环磷腺苷（dbcAMP）可使I Ba(max)增加37%，而该作用可被Rp-cAMPs消除；佛波醇酯（PMA）可使电流降低32%，该作用可被星形孢菌素消除。NE可使原本I Ba(max)相对较小的细胞的I Ba(max)增加，使I Ba(max)较大的细胞的电流降低。在酚妥拉明存在的情况下，NE可使I Ba(max)增加，且这种作用在I Ba(max)较小的细胞中更为显著。在普萘洛尔存在的情况下，NE可使I Ba(max)降低。Rp-cAMPs可消除兴奋性β-肾上腺素能受体激活的作用，星形孢菌素可消除抑制性α-肾上腺素能受体的作用。提示NE对豚鼠输精管平滑肌的L型钙通道具有双重（兴奋和抑制）作用。通过环磷腺苷/蛋白激酶A（cAMP/PKA）介导的兴奋性β-肾上腺素能受体作用在钙通道密度较低的细胞中占主导地位，而通过蛋白激酶C（PKC）介导的抑制性α-肾上腺素能受体作用在通道密度较高的细胞中占主导地位。
