Improve Morphological Changes and Reduce Vasospasm by Treatment with Selective Endothelin- converting Enzyme Inhibitor Following Experimental Subarachnoid Hemorrhage

• Main Author: 吳淑釧
• Other Authors: 關皚麗
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/57750690512237485790

碩士 === 高雄醫學大學 === 醫學研究所 === 90 === Endothelin-1（ET-1）is a potent vasoconstrictor that has been implicated in the pathogenesis of cerebral vasospasm after SAH. Endothelin-1（ET-1）is synthesized initially as a large prepropeptide that requires multiple steps of post-translational processing for activation. The final step of this processing involves the proteolytic cleavage of a relatively inactive precursor, big Endothelin-1 （big ET-1）, by the metalloprotease endothelin-converting enzyme （ECE）. Previous studies have demonstrated that endothelin-converting enzyme inhibitor （CGS 26303）could prevent and reverse arterial narrowing in a rabbit model of subarachnoid hemorrhage（SAH）. However, attenuation of vasospastic response was incomplete and required relatively high dose to be effective in reversing vasospasm. Therefore, the first study was designed to examined the effects of a highly selective endothelin-converting enzyme inhibitor, CGS 35066, in the preventing SAH-induced cerebral vasospasm in rabbit model. The ultrastructural changes of mitochondria and endothelial cells of basilar arteries were examined by Transmission Electron Microscopy（TEM）. The reasons why we adapt experiments with rats are comely product just produced from rabbit anti-Endothelin-1 serum and highly selective Endothelin-converting enzyme inhibitor CGS 35066 was difficult to be purified and available. Therefore，the second study planned to another use the Endothelin-converting enzyme inhibitor CGS 26303 in Sprague-Dawley Rat model. In prevention and reversion study，we examined the expression of ET-1 in the basilar arteries of experiment rats with the immunohistochemical stain. Via the use of Transmission Electron Microscopy（TEM）， the ultrastructure was different between the SAH and treatment groups. This gave us an information whether to evaluate the relationship between Endothelial cells change and Endothelin-converting enzyme inhibitor under TEM？ （A）New Zealand white rabbits were subjected to experimental SAH by injecting autogenous blood into the cisterna magna. Endothelin-converting enzyme inhibitor CGS 35066（10 mg/kg）or vehicle was injected intravenously twice daily for two days initially at 1 hour after SAH. Animals were divided into the following seven groups： （1）control（no SAH）；（2）2 days after SAH（no treatment）；（3）7 days after SAH（no treatment）；（4）2 days after SAH＋CGS 35066；（5）7 days after SAH＋CGS 35066；（6）2 days after SAH＋Vehicle；（7）7 days after SAH＋Vehicle. Animals were sacrificed by perfusion fixation 7 days post-SAH. Basilar arteries were removed, sectioned and stained. The ultrastructural changes of mitochondria and endothelial cells were examined by Transmission Electron Microscopy （TEM）. Our results showed that corrugation of endothelial cells and destruction of endothelial cells and mitochondria were obvious in 2 days after SAH and 2 days after SAH＋vehicle animals. In 7days after SAH only animals, no more corrugation of endothelial cells was found, but endothelial cells and mitochondria were severely damaged. However, endothelin-converting enzyme inhibitor CGS 35066 could reserve the intact endothelial cells and mitochondria at 2 days and 7 days after SAH. These finding indicate that intravenous injection of highly selective endothelin-converting enzyme inhibitor can prevent endothelial cells and mitochondrial damage after SAH. Endothelin-converting enzyme inhibitor CGS 35066 can be an alternative approach in the treatment of SAH-induced vasospasm. （B） Reduce level of ET-1 can attenuate vasospastic response. Intravenous infusion of CGS 26303 at doses of 0.24, 0.8, or 2.4 mg/100g/d was initiated 1 hour after SAH in Sprague-Dawley Rat. In prevention study animals were divided into the following six groups： （1）control（no SAH）；（2）SAH only（no treatment）；（3）SAH＋2.4 mg/100 g/d CGS 26303；（4）SAH＋0.8 mg/100 g/d CGS 26303；（5）SAH＋0.24 mg/100 g/d CGS 26303 ；（6）SAH＋Vehicle. In reverse study animals were divided into the following six groups： （1）control（no SAH）； （2） SAH only（no treatment）；（3）SAH＋2.4 mg/100 g/d CGS 26303；（4）SAH＋0.8 mg/100 g/d CGS 26303；（5）SAH＋0.24 mg/100 g/d CGS 26303 ；（6）SAH＋Vehicle. The same procedure was repeated 48 hours after the first experimental SAH. One week later, all animals were killed. Basilar arteries were removed, ET-1 immunohistochemical stain was applied, embedded and sectioned, observed with T.E.M. Dose related attenuation to the positive staining was noticed when compared with SAH only.