Villalba Nuria, Stankevicius Edgaras, Simonsen Ulf, Prieto Dolores
Dept. de Fisiología, Facultad de Farmacia, Univ. Complutense, 28040-Madrid, Spain.
Am J Physiol Heart Circ Physiol. 2008 Apr;294(4):H1923-32. doi: 10.1152/ajpheart.01221.2007. Epub 2008 Jan 25.
Tonic physiological activity of RhoA/Rho kinase contributes to the maintenance of penile flaccidity through its involvement in the Ca(2+) sensitization of erectile tissue smooth muscle. The present study hypothesized that Rho kinase is also involved in the modulation of Ca(2+) entry induced by alpha(1)-adrenoceptor stimulation of penile arteries. Rat penile arteries were mounted in microvascular myographs for simultaneous measurements of intracellular Ca(2+) (Ca(2+)) and force. The Rho-kinase inhibitor Y-27632 markedly reduced norepinephrine-mediated electrically induced contractions and the increases in both Ca(2+) and tension elicited by the alpha(1)-adrenoceptor agonist phenylephrine (Phe). In contrast, the protein kinase C (PKC) inhibitor Ro-31-8220 reduced tension without altering the Phe-induced increase in Ca(2+). In the presence of nifedipine, Y-27632 still inhibited the non-L-type Ca(2+) signal and blunted Phe contraction. Y-27632 did not impair the capacitative Ca(2+) entry evoked by store depletion with cyclopiazonic acid but largely reduced the Ba(2+) influx stimulated by Phe in fura-2 AM-loaded arteries. The addition of Y-27632 to arteries depolarized with high KCl markedly reduced tension without changing Ca(2+). In alpha-toxin-permeabilized penile arteries stimulated with threshold Ca(2+) concentrations, Y-27632 inhibited the sensitization induced by either guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) or Phe in the presence of GTPgammaS. However, Y-27632 failed to alter contractions induced by a maximal concentration of free Ca(2+). These results suggest that Rho kinase, besides its contribution to the Ca(2+) sensitization of the contractile proteins, is also involved in the regulation of Ca(2+) entry through a nonselective cation channel activated by alpha(1)-adenoceptor stimulation in rat penile arteries.
RhoA/Rho激酶的紧张性生理活动通过参与勃起组织平滑肌的Ca(2+) 敏感性来维持阴茎的疲软状态。本研究假设，Rho激酶也参与调节由阴茎动脉α(1)-肾上腺素能受体刺激诱导的Ca(2+) 内流。将大鼠阴茎动脉安装在微血管肌动描记器中，用于同时测量细胞内Ca(2+) (Ca(2+)) 和张力。Rho激酶抑制剂Y-27632显著降低去甲肾上腺素介导的电诱导收缩以及由α(1)-肾上腺素能受体激动剂苯肾上腺素 (Phe) 引起的Ca(2+) 和张力的增加。相比之下，蛋白激酶C (PKC) 抑制剂Ro-31-8220降低了张力，但未改变Phe诱导的Ca(2+) 增加。在硝苯地平存在的情况下，Y-27632仍抑制非L型Ca(2+) 信号并减弱Phe收缩。Y-27632不损害由环匹阿尼酸耗尽储存所诱发的容量性Ca(2+) 内流，但在fura-2 AM负载的动脉中，很大程度上减少了Phe刺激的Ba(2+) 内流。向用高KCl去极化的动脉中添加Y-27632显著降低张力，而不改变Ca(2+)。在用阈值Ca(2+) 浓度刺激的α-毒素通透的阴茎动脉中，Y-27632在存在鸟苷5'-O-(3-硫代三磷酸) (GTPγS) 的情况下抑制由GTPγS或Phe诱导的敏感性。然而，Y-27632未能改变由最大浓度的游离Ca(2+) 诱导的收缩。这些结果表明，Rho激酶除了对收缩蛋白的Ca(2+) 敏感性有贡献外，还通过大鼠阴茎动脉中由α(1)-肾上腺素能受体刺激激活的非选择性阳离子通道参与Ca(2+) 内流的调节。
