Park J M, Borer J G, Freeman M R, Peters C A
Urologic Laboratory, Department of Urology, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
Am J Physiol. 1998 Nov;275(5):C1247-54. doi: 10.1152/ajpcell.1998.275.5.C1247.
Cultured rat bladder smooth muscle cells (SMC) were grown on collagen-coated silicone membranes and subjected to continuous cycles of stretch-relaxation. Semiquantitative RT-PCR analysis revealed a time-dependent increase in heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) mRNA levels after stretch, with maximal levels appearing after 4 h. Immunostaining for proHB-EGF revealed higher levels of HB-EGF protein in the stretched than in the nonstretched SMC. The ANG II receptor type 1 antagonist losartan markedly suppressed stretch-activated HB-EGF expression. ANG II levels were 3.3-fold higher in the stretch- than in the non-stretch-conditioned media. Stretch stimulation of bladder SMC that had been transiently transfected with an HB-EGF promoter-luciferase expression construct resulted in an 11-fold increase in reporter activity. Mechanical stretch induced a 4.7-fold increase in tritiated thymidine incorporation rate, and this was reduced by 25% in the presence of losartan. We conclude that mechanical stretch activates HB-EGF gene expression in bladder SMC and that this is mediated in part by autocrine ANG II secretion.
将培养的大鼠膀胱平滑肌细胞（SMC）接种于包被胶原的硅酮膜上，并使其经历持续的拉伸-松弛循环。半定量逆转录-聚合酶链反应（RT-PCR）分析显示，拉伸后肝素结合表皮生长因子（EGF）样生长因子（HB-EGF）mRNA水平呈时间依赖性增加，4小时后达到最高水平。对前体HB-EGF进行免疫染色显示，拉伸的SMC中HB-EGF蛋白水平高于未拉伸的SMC。1型血管紧张素II（ANG II）受体拮抗剂氯沙坦可显著抑制拉伸激活的HB-EGF表达。拉伸条件培养基中的ANG II水平比未拉伸条件培养基中的高3.3倍。用HB-EGF启动子-荧光素酶表达构建体瞬时转染的膀胱SMC经拉伸刺激后，报告基因活性增加了11倍。机械拉伸使氚标记胸腺嘧啶核苷掺入率增加了4.7倍，在氯沙坦存在的情况下，该掺入率降低了25%。我们得出结论，机械拉伸可激活膀胱SMC中HB-EGF基因的表达，且这部分是由自分泌的ANG II分泌介导的。
