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研究生:林春月
研究生(外文):Lin, Chun-Yueh
論文名稱:切除六分之五腎臟的慢性尿毒症大鼠腎臟處理硒的研究
論文名稱(外文):Renal handling of selenium in rats with chronic uremia induced by 5/6 nephrectomy
指導教授:楊志剛楊志剛引用關係
指導教授(外文):Young, Tze-Kong
學位類別:碩士
校院名稱:國立陽明大學
系所名稱:生理學研究所
學門:醫藥衛生學門
學類:醫學學類
論文種類:學術論文
論文出版年:1997
畢業學年度:85
語文別:中文
論文頁數:65
中文關鍵詞:生理學慢性尿毒症
外文關鍵詞:PHYSIOLOGY
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硒(Selenium)是生物體生長所必需的微量元素之一。主要的生理作用是作為穀胱甘汰過氧化酉每的輔因子,此酉每對清除體內自由基的作用,佔有很重要的角色。由於食入的硒大約有50%∼70%是經由腎臟排出,因此可知腎臟對生物體內硒的恆定扮演很重要的角色。有許多研究指出,慢性腎衰竭的病人有血漿硒濃度下降的情形,而至今其機轉仍不明。本實驗的目的乃是利用切除六分之五腎臟的方法所誘發的慢性尿毒症大鼠,探討在平常血漿硒濃度及增加血漿硒濃度的二種情況下,其腎臟對硒的處理情形與正常鼠有何不同。
實驗是使用雄性Sprague-Dawley種系的大白鼠,分為正常及切除5/6腎臟的慢性尿毒二組。在實驗的前一天,將動物置於新陳代謝籠中,經禁食但飲水不受限制的清醒情況下,收集24小時尿液檢體。實驗當日,以戊巴比妥鈉麻醉動物,經插管及收集血液檢體。之後,從胃及靜脈灌注溶液誘發其利尿狀況,於達平衡後,經由股靜脈灌注三種不同劑量的亞硒酸鈉以逐步提高大鼠血中硒的濃度。經一段時間待體內硒濃度達穩定後,收集血液及尿液檢體︰以菊糖清除率來代表腎絲球濾過速率,血漿經超濾過膜過濾,以模擬腎絲球的過濾液。所有檢體的晒硒度以石墨原子吸光儀測定之。
在清醒狀況下,切除5/6腎臟的尿毒組,其血漿尿素氮、肌酸酐及滲透度均較正常組者為高,而肌酸酐清除率則顯著低於正常組者。另外,尿毒症鼠血漿硒濃度下降,顯示有缺硒的情形。上述結果顯示,此方法所誘發的尿毒症鼠為研究尿毒病人血漿硒濃度下降的可用動物模式之一。此外,實驗結果發現二組實驗動物的尿蛋白、肌酸酐及尿素氮排泄與尿硒排泄間皆呈現有統計上顯著的正相關。而且尿毒症鼠的24小時尿液排泄硒的量與正常組者相比有顯著的增加。
在尿流量增加的利尿期,此時二組實驗動物的尿硒排泄與尿流量也呈現有顯著性的正相關。在人為地提高血漿硒濃度的情況下,隨血漿硒濃度的增加,腎絲球濾過下來硒的量及尿中排泄硒的量隨之增加,此現象在兩組皆是。將腎絲球濾過硒量減去尿中排泄硒量得到腎小管再吸收量,同發現尿毒組再吸收硒的量顯著的低於正常組。此外,將再吸收硒的量換算為再吸收分率,結果可發現在三種劑量下,尿毒組的再吸收分率皆顯著的低於正常組,而隨著血漿硒濃度的升高,尿毒組的排泄分率也顯著的高於正常組。因此本實驗結論為:尿毒症鼠硒缺乏的原因,主要可能是由於其殘存腎臟的腎小管再吸收硒的能力減低所致。
Selenium (Se) is an essential trace element for animals and humans. It is an integral component of the ubiquitous enzyme glutathione peroxidase, an antioxidant that destroys harmful peroxides produced during metabolic processes. It is well documented that patients with chronic uremia have lower plasma Se levels than normal subjects. Since about 50 % - 70 % of the Se consumed is excreted in the urine, the kidney may play an important role in the pathogenesis of such Se deficiency in chronic uremia.
The aim of this study was to investigate renal handling of selenium in rats with chronic uremia either with or without Se loading. Uremia was experimentally induced by 2-stage five-sixths nephrectomy in male Sprague-Dawley rats. Three weeks after the second operation, rats were anesthetized with pentobarbital. Blood and timed urine samples were collected for determination of urea nitrogen, creatinine, and inulin. Total and ultrafiltrable plasma and urine selenium concentrations were determined by a graphite furnace atomic absorption spectrophotometer. The total plasma selenium concentration in uremic rats was found to be 0.45 ±0.04 μg/mL, which was significantly less than 0.55 ±0.04 μg/mL found in normal rats. In contrast, urinary excretion of Se was significantly greater in uremic rats. Urinary excretion of Se significantly correlated to urinary excretion of protein and urine flow rate in both groups of rats. Urinary excretion of Se also correlated to urinary excretion of urea nitrogen and creatinine in normal rats.
Using inulin clearance to represent glomerular filtration rate, the filtered load and fractional excretion of selenium were thus calculated when the plasma selenium concentration was stepwise increased by intravenous infusion of sodium selenite at different doses. It was found that fractional excretion of selenium increased with increment of plasma selenium concentration in both normal and uremic rats. Moreover, fractional Se excretion was significantly greater in uremic rats than in normal rats at any given plasma selenium concentration tested. This finding indicates that tubular reabsorption of selenium is impaired and may account for the decrease of plasma selenium concentration, observed in this uremia rat model.
In summary, tubular reabsorption of selenium was significantly decreased in uremic rats three weeks after 5/6 nephrectomy.

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