Zimmermann Michael, Jung Carla Sabine, Vatter Hartmut, Raabe Andreas, Seifert Volker
Department of Neurosurgery, University of Frankfurt/Main, Schleusenweg 2-16, 60528 Frankfurt, Germany.
Neurosurg Rev. 2003 May;26(2):125-32. doi: 10.1007/s10143-002-0242-9. Epub 2002 Nov 19.
The aim of this study was to investigate whether the blocking of endothelin-converting enzyme (ECE) activity offers a new approach to inhibiting the development of cerebral vasospasm after subarachnoid hemorrhage (SAH) by preventing transformation of big endothelin-1 (big ET-1) to vasoactive endothelin-1 (ET-1). The effect of potential ECE inhibitors was determined in vitro by measurement of isometric contractions, induced by big ET-1, in isolated rat basilar arteries. Intact and de-endothelialized endothelium (E+ and E-, respectively) segments were examined after preincubation with the putative ECE inhibitors: phosphoramidon (10(-4) M), and [22D-Val]big ET-1 [16-38] (10(-5) M and 10(-6) M). Additionally, the effect of [D-Val22]big ET-1 [16-38] was investigated in rabbits after intracisternal application in order to inhibit the contraction of the basilar artery induced by (2x10(-6) M) big ET-1. Application of 10(-4)-M phosphoramidon resulted in a statistically significant decrease in big ET-1-induced contraction in E+ and E- segments; 10(-5)-M and 10(-6)-M [22D-Val]big ET-1 [16-38] in E- segments produced no statistically significant effect. The application of 10(-6)-M [22D-Val]big ET-1 [16-38] in E+ segments caused increased contractions, as shown by the shift to the left of the concentration-effect curve (CEC). In the rabbit group pretreated with [D-Val22]big ET-1 [16-38] (2x10(-5) M) (n=8), the angiographically measured diameter of the basilar artery increased from 0.63+/-0.12 mm to 0.66+/-0.12 mm. In the control group (n=8), this diameter decreased from 0.71+/-0.13 mm to 0.57+/-0.15 mm. This corresponded to an increase in vessel diameter of 5.24+/-9.89% in the treatment group and a decrease of 19.54+/-15.81% in the control group (P=0.002). The present study indicates the existence of functional ECE activity in rat basilar artery, which differs in the endothelium and the smooth muscle layer. These results demonstrate that [D-Val22]big ET-1 [16-38] has a potent ECE-inhibitory effect, preventing cerebral vasospasm in rabbit basilar artery by inhibiting the transformation of big ET-1 to vasoactive ET-1 after intracisternal application in vivo, whereas no inhibitory effect was detectable in rat basilar artery in vitro. Therefore, further studies of the biochemical nature of cerebrovascular ECE activity are required.
本研究的目的是探讨通过阻止大内皮素 -1（big ET-1）转化为血管活性内皮素 -1（ET-1）来阻断内皮素转化酶（ECE）活性是否为抑制蛛网膜下腔出血（SAH）后脑血管痉挛发展提供了一种新方法。通过测量大ET-1诱导的离体大鼠基底动脉等长收缩，在体外确定潜在ECE抑制剂的作用。在用假定的ECE抑制剂：磷酰胺（10⁻⁴ M）和[22D-Val]big ET-1 [16 - 38]（10⁻⁵ M和10⁻⁶ M）预孵育后，检查完整和去内皮的内皮（分别为E+和E-）节段。此外，为了抑制（2×10⁻⁶ M）大ET-1诱导的基底动脉收缩，在兔脑池内应用后研究了[D-Val22]big ET-1 [16 - 38]的作用。应用10⁻⁴ M磷酰胺导致E+和E-节段中大ET-诱导的收缩在统计学上显著降低；E-节段中10⁻⁵ M和10⁻⁶ M的[22D-Val]big ET-1 [16 - 38]未产生统计学上显著的作用。E+节段中应用10⁻⁶ M的[22D-Val]big ET-1 [16 - 38]导致收缩增加，浓度 - 效应曲线（CEC）向左移动表明了这一点。在用[D-Val22]big ET-1 [16 - 38]（2×10⁻⁵ M）预处理的兔组（n = 8）中，血管造影测量的基底动脉直径从0.63±0.12 mm增加到0.66±0.12 mm。在对照组（n = 8）中，该直径从0.71±0.13 mm减小到0.57±0.15 mm。这对应于治疗组血管直径增加5.24±9.89%，对照组减小19.54±15.81%（P = 0.002）。本研究表明大鼠基底动脉中存在功能性ECE活性，其在内皮和平滑肌层有所不同。这些结果表明，[D-Val22]big ET-1 [16 - 38]具有强大的ECE抑制作用，在体内脑池内应用后通过抑制大ET-1转化为血管活性ET-1来预防兔基底动脉中的脑血管痉挛，而在体外大鼠基底动脉中未检测到抑制作用。因此，需要进一步研究脑血管ECE活性的生化性质。
