高血壓是人類常見疾病之一，其作用機轉非常複雜。而中樞神經系統的延腦鼻端腹外側核經由感壓反射和強直性興奮交感神經系統兩種機轉，來維持血壓和心跳穩定。反應性氧族是由嗜氧細胞所產生之氧分子或其衍生物所組成之家族，可造成氧化壓力。文獻指出，超氧陰離子可引發高血壓。超氧化物岐化酶是細胞抵禦氧化壓力最重要的酶類之一，主要是將超氧陰離子催化成氧氣和過氧化氫。一氧化氮是精胺酸經由一氧化氮合成酶以及NADPH輔酶合成的氣體分子。一氧化氮在延腦鼻端腹外側核區對心血管的影響，主要是透過調節神經傳導物質的釋放而改變自主神經系統的活性，參與調控血壓和心跳。雖然氧化壓力與一氧化氮在文獻中均有報導，指出其參與心臟血管功能調控，然而此兩分子物質如何相互作用，在延腦鼻端腹外側核參與中樞調控心臟血管功能，則有待進一步了解。
本實驗以微量注射腺病毒載體AdeNOS (Adenoviral vectors encoding endothelial nitric oxide synthase)，AdSOD2 (Adenoviral vectors encoding superoxide dismutase 2)或合併AdeNOS與AdSOD2於正常血壓Wistar-Kyoto (WKY)或自發性高血壓spontaneously hypertensive rats (SHR)的雙側延腦鼻端腹外側核區，觀察大鼠心血管系統的長期變化。結果顯示：1. 微量注射腺病毒載體AdeNOS於SHR或WKY兩組大鼠的雙側延腦鼻端腹外側核區中，可以明顯降低兩組大鼠血壓和心跳。根據先前研究結果，推測是eNOS經由增加GABAergic神經傳導，降低大鼠自主神經系統的活性而產生。SHR組的血壓下降幅度大於WKY組，可能的原因是SHR大鼠的延腦鼻端腹外側核區中，原存有之一氧化氮的含量低於WKY組所致。而SHR組大鼠的血壓於給予病毒後第28天反彈高於基準值，推測與SHR大鼠的延腦鼻端腹外側核區超氧陰離子濃度較高，造成一氧化氮活性減低有關。2. 微量注射腺病毒載體AdSOD2於SHR或WKY兩組大鼠的雙側延腦鼻端腹外側核區中，只能使SHR組血壓下降，對WKY大鼠之基礎血壓，與SHR 或WKY大鼠心跳沒有影響。其原因可能是SHR大鼠延腦鼻端腹外側核區產生的超氧陰離子濃度過高，或是抗氧化壓力的酶類功能不正常，因此當加入外來的SOD2時，可以代謝過多超氧陰離子，減少氧化壓力，進而降低血壓。3. 合併微量注射腺病毒載體AdeNOS與AdSOD2於雙側延腦鼻端腹外側核區，發現在SHR大鼠上，可產生比單獨注射AdeNOS組或AdSOD2組更大幅度地降血壓作用；而且血壓下降的時效，至少延長至第28天。我們推論是SOD2可以清除超氧陰離子，使超氧陰離子不能和一氧化氮結合，延長一氧化氮的半衰期，增加一氧化氮的功能。
綜合本研究所得結果，推論一氧化氮在延腦鼻端腹外側核區中樞調節心血管功能中扮演重要角色，並且一氧化氮活性衰竭可能是造成高血壓原因之一；另一方面在SHR高血壓大鼠延腦鼻端腹外側核區，較多的氧化壓力也是引起高血壓之重要原因。根據研究結果進一步推論，超氧陰離子在延腦鼻端腹外側核區參與高血壓之角色有雙重，其一為引起氧化傷害，另一則為與一氧化氮產生反應，降低原本已不足之一氧化氮活性，使高血壓持續維持。

The dissection of etiology of hypertension is a medical imperative. In the central nervous system, rostral ventral lateral medulla (RVLM) plays an essential role in the maintenance of arterial pressure and heart rate through tonic activation of the sympathetic vasomotor activity and regulation of baroreflex response. Oxidative stress of an enhanced cellular content of the reactive oxygen species, in particular the superoxide anion (O2-), has been implicated in hypertension. Superoxide dismutase (SOD) is one of the most important defense enzymes against the oxidative stress through catalysis of O2- into O2 and H2O2. SOD treatment has been demonstrated to decrease arterial pressure. Moreover, in addition to its peripheral vasodilatory effect, nitric oxide (NO) plays an active role in central regulation of arterial pressure and heart rate via modulation of the autonomic system. In the RVLM, both O2- and NO have been demonstrated to be involved in hypertension. Interactions between these two molecules, however, are not understood. The aims of this study are therefore to establish the significance of O2- and NO in the RVLM on blood pressure regulation in hypertension and to examine whether O2- interacts with NO to participate in the pathogenesis of hypertension.
To examine their long term effects on mean systemic arterial pressure (MSAP) and heart rate (HR), SOD and/or NO was over-expressed by microinjection of the adenoviral vectors encoding the endothelial NO synthase (AdeNOS) and/or mitochondrial SOD (AdSOD2) into RVLM of the normotensive Wistar-Kyoto (WKY) rats or the spontaneously hypertensive rats (SHR). I found that microinjection of AdeNOS in the RVLM of SHR or WKY rats significantly decreased MSAP or HR that lasted for around 10 days postinjection. The hypotensive effect of AdeNOS was significantly greater in SHR than WKY rats. The AdeNOS-promoted hypotension in SHR, but not WKY rats, was followed by a rebound hypertension, detected in 28 days after the gene transfer. In the AdeSOD2-treated animals, I found a significant decrease in the MSAP in SHR, but not WKY rats, that lasted for about 7 days postinjection. On the other hand, no change in HR was detected in either SHR or WKY rats after the AdSOD2 gene transfer into the RVLM. In animals that received co-microinjection into the bilateral RVLM of AdeNOS and AdSOD2, there was a further prolonged decrease in MSAP or HR in SHR. The rebound hypertension observed in the AdeNOS-treated SHR was reversed to hypotension in the AdeNOS+AdSOD2-treated SHR. There was no difference in the hypotensive or bradycardiac effects in WKY rats that received the AdeNOS+AdSOD2 or AdeNOS gene transfer.
Together these results suggest that (1) NO in RVLM plays an important role in central regulation of arterial pressure and heart rate under both normotensive and hypertensive conditions. A greater reduction in MSAP in the AdeNOS-treated SHR further indicates a reduced action of NO at the RVLM in the pathogenesis of hypertension. (2) An excessive oxidative stress of a reduced function of SOD2 in RVLM may be an important factor in neural mechanism of hypertension in SHR. The same mechanism, at the same time, may underlie the rebound hypertensive observed in the AdeNOS-treated SHR. (3) The excessive oxidative stress in the RVLM contributes to hypertension by at least two mechanisms. One is to cause oxidative injury in the RVLM and the other is to interact with NO to decrease already insufficient activity of NO in central cardiovascular regulation.

正文目錄

頁次
第一章 緒 論 10
第二章 研究動機與目的 21
第三章 實驗材料和方法 24
第四章 實驗結果 29
第五章 討論 38
第六章 結論 46
第七章 未來研究方向 49
參考文獻 51
附圖 58

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