支链氨基酸对运动大鼠和小鼠蛋白质代谢的影响

目的 :　探讨在运动状态下 ,支链氨基酸 ( BCAA)对大鼠和小鼠蛋白质代谢的影响。方法 :　利用15N-甘氨酸稳定同位素作为示踪剂 ,观察动物在游泳运动条件下的氮平衡、氨基氮流率、蛋白质合成率和分解率 ,以及心肌、肝脏、股四头肌的蛋白质代谢状况。结果 :　补充 BCAA使整体氨基氮流率、蛋白质合成率、更新率有不同程度增高 ;BCAA可调节运动对心肌、肝脏蛋白质代谢的影响 ,使骨骼肌的氨基氮流率增高明显。结论 :　补充 BCAA可调节运动状态下机体蛋白质代谢 ,使运动状态的骨骼肌氨基氮流率增高。     

全小肠切除术后蛋白质代谢随访研究

本文对１例全小肠切除术后经静脉营养维持生存９年余的病人，通过口服稳定同位素１５Ｎ－赖氨酸及１５Ｎ－甘氨酸和同位素９９Ｔｃ－ＤＴＰＡ－ＨＳＡ白蛋白，测定其对氨基酸及蛋白质的吸收代谢情况，并以此结果与５年前的检测结果进行比较。结果发现，病人在口服氨基酸后...     

营养

022333支链氨基酸对运动大鼠和小鼠蛋白质代澍的影响/许志勤…//营养学报.一2001,23(2).一102～105 探讨在运动状态下,支链氨基酸(BCAA)对大鼠和小鼠蛋白质代谢的影响。利用”N一甘氨酸稳定同位素作为示踪剂,观察动物在游泳运动条件下的氮平衡、氨基氮流率、蛋白质合成率和分解     

15N-甘氨酸在大鼠蛋白质代谢研究中给药剂量与方法的探讨

目的:用15N-甘氨酸作为示踪剂,探索在大鼠蛋白质代谢实验中,15N-甘氨酸的用药荆量和方法.方法:实验以大鼠游泳为动物模型,观察了15N-甘氨酸的一次用药和连续多次用药方法的不同变化,以及4个用药剂量的差别.结果:观察大鼠整体蛋白质代谢情况,应采用多次灌胃方法;用药剂量在4～6mg·100g-1BW之间为宜.实际结果还显示,两组动物均为正氮平衡,运动组平均每天体重增长1.75 g,正常组为2.77 g.结论:将示踪法用于大鼠蛋白质代谢的研究所得结果,较单纯使用氨平衡方法更加深入、准确.     

气质联用分离测定^15N—苷氨酸方法的研究

使用小型气质联用仪测定了血清中＾１５Ｎ－甘氨酸丰度值，利用代数法分析质谱重叠碎片峰数据，计算得理论值与实际丰度值成线性相关，其相关系数可达０．９９９２，选用健康Ｗｉｓｔａｒ大鼠一次灌胃＾１５Ｎ－甘氨酸２０ｍｇ，用该方法测定灌胃前，灌胃后３０ｍｉｎ及１ｈ至７ｈ血清中＾１５Ｎ－甘氨酸中的丰度值，绘制＾１５Ｎ－甘氨酸含量随时间衰变曲线，结果表明，该方法适用于医学研究中低丰度样品的测定，为稳定同位素丰度测     

气质联用分离测定~(15)N-甘氨酸方法的研究

使用小型气质联用仪测定了血清中１５Ｎ－甘氨酸丰度值，利用代数法分析质谱重叠碎片峰数据，计算得理论值与实际丰度值成线性相关，其相关系数可达０．９９９２。选用健康Ｗｉｓｔｅｒ大鼠一次灌胃１５Ｎ－甘氨酸２０ｍｇ，用该方法测定灌胃前、灌胃后３０ｍｉｎ及１ｈ至７ｈ血清中１５Ｎ－甘氨酸的丰度值，绘制１５Ｎ－甘氨酸含量随时间衰变曲线，结果表明，该方法适用于医学研究中低丰度样品的测定，为稳定同位素丰度测定提供了一个更准确简便的分析方法。     

^15N—甘氨酸在大鼠蛋白质代谢研究中给药剂量与方法？…

目的用15N-甘氨酸作为示踪剂,探索在大鼠蛋白质代谢实验中,15N-甘氨酸的用药荆量和方法.方法实验以大鼠游泳为动物模型,观察了15N-甘氨酸的一次用药和连续多次用药方法的不同变化,以及4个用药剂量的差别.结果观察大鼠整体蛋白质代谢情况,应采用多次灌胃方法;用药剂量在4～6mg·100g-1BW之间为宜.实际结果还显示,两组动物均为正氮平衡,运动组平均每天体重增长1.75 g,正常组为2.77 g.结论将示踪法用于大鼠蛋白质代谢的研究所得结果,较单纯使用氨平衡方法更加深入、准确.     

膳食乳清蛋白和酪蛋白对大鼠肾钙质沉着作用的比较

本实验研究了不同水平的乳清蛋白和酪蛋白对雌性断乳大鼠肾钙质沉着（ＮＣ）作用的影响。饲料氮水平为２．４％（蛋白质１５％）时，乳清蛋白可显著降低大鼠ＮＣ的发生率。氮水平为４．８％（蛋白质３０％）时，酪蛋白也降低了大鼠ＮＣ的发生率，而乳清蛋白组大鼠未见到ＮＣ的发生。以１５％与酪蛋白和乳清蛋白组成相似的氨基酸混合物给大鼠，不影响ＮＣ的发生率；当氨基酸混合物增至３０％，可降低ＮＣ的发生率。结果提示：不同种类蛋白质影响大鼠肾钙质沉着与其氨基酸的组成无关，而可能与蛋白质的结构或某些非蛋白质组分有关。     

谷氨酰胺对严重烧伤小型香猪肠道物质代谢功能的影响

本文采用小型香猪烧伤模型，通过肠系膜下静脉、门静脉、髂动脉插管，从不同部位采取血标本，结合门静脉流量测定，动态观察了烧伤早期肠道营养以及补充谷氨酰胺对肠道物质代谢功能的影响。动物随机为两组，ＧＬＮ组和ＮＯＮ－ＧＬＮ组。时相点为伤前、伤后第一、四、七、十天及进食后１５，３０，４５和６０ｍｉｎ。实验结果提示：（１）烧伤早期肠道对葡萄糖的利用明显减少；（２）烧伤后期，肠道利用谷氨酰胺增加，减少了少葡萄糖     

膳食蛋白质水平及含硫氨基酸对人体钙代谢的影响

目的：了解在我国实际膳食情况下，增加蛋白质摄入量对钙代谢的影响。方法：７名２４～３１岁的健康男性青年于４个实验期中分别轮流摄取四种不同的膳食，包括：基础膳食；基础膳食加４０ｇ鸡蛋白蛋白质；基础膳食加蛋氨酸１．９ｇ和胱氨酸１．７ｇ；以及基础膳食加牛磺酸２．４ｇ。然后观察尿钙、钙吸收及钙平衡的变化。结果：各膳食期钙的表观吸收率均无差异，补充蛋白质或补充蛋氨酸和胱氨酸使尿硫酸根及尿钙排泄量显著高于基础膳食期，并且钙平衡也均降低。补充牛磺酸对尿钙和钙平衡均无影响。结论：高蛋白质摄入对钙平衡的负面影响与含硫氨基酸蛋氨酸和胱氨酸的分解产物硫酸根排出增加有关     

蛋白质与锌不同摄入水平对大鼠锌吸收与存留影响的研究

WAK纯品系断奶雄大鼠30只,随机分为6组。喂纯合成饲料。第1、2、3组饲料含锌分别为6、15和24ppm,含蛋白质均为10％。第4、5、6组饲料含蛋白质分别为5％、10％和20％,含锌量均为15ppm。喂养50天后按体重每100g灌胃~(65)Zn 1.5μCi,即日起连续收集5天粪尿,用~(65)Zn示踪法测定各组动物锌吸收与存留情况。结果表明:低锌组大鼠锌吸收率与存留率显著增高;低蛋白组大鼠锌吸收率与存留率显著降低,提高蛋白质摄入水平可明显改善锌的吸收与存留;大鼠尿锌排出率很低,作为研究锌代谢指标的意义不大。本文并对锌吸收与存留的测定方法进行了讨论。     

NITROGEN INTAKE AND TUMORIGENESIS IN RATS

Adenocarcinomas of small and large intestine were larger in gross appearance and significantly more numerous in rats fed 15 and 22.5 percent dietary protein compared with animals fed 7.5 percent protein.
All animals received DMH, a carcinogenic stimulating substance producing intestinal tumors in rats.     

Incorporation of urea and ammonia nitrogen into ileal and fecal microbial proteins and plasma free amino acids in normal men and ileostomates

BACKGROUND: The importance of urea nitrogen reutilization in the amino acid economy of the host remains to be clarified. OBJECTIVE: The objective was to explore the transfer of (15)N from orally administered [(15)N(2)]urea or (15)NH(4)Cl to plasma free and intestinal microbial amino acids. DESIGN: Six men received an L-amino acid diet (167 mg N*kg(-)(1)*d(-)(1); 186 kJ*kg(-)(1)*d(-)(1)) for 11 d each on 2 different occasions. For the last 6 d they ingested [(15)N(2)]urea or, in random order, (15)NH(4)Cl (3.45 mg (15)N*kg(-)(1)*d(-)(1)). On day 10, a 24-h tracer protocol (12 h fasted/12 h fed) was conducted with subjects receiving the (15)N tracer hourly. In a similar experiment, (15)NH(4)Cl (3.9 mg (15)N*kg(-)(1)*d(-)(1)) was given to 7 ileostomates. (15)N Enrichments of urinary urea and plasma free and fecal or ileal microbial protein amino acids were analyzed. RESULTS: (15)N Retention was significantly higher with (15)NH(4)Cl (47.7%; P < 0.01) than with [(15)N(2)]urea (29.6%). Plasma dispensable amino acids after the (15)NH(4)Cl tracer were enriched up to 20 times (0. 2-0.6 (15)N atom% excess) that achieved with [(15)N(2)]urea. The (15)N-labeling pattern of plasma, ileal, and fecal microbial amino acids (0.05-0.45 (15)N atom% excess) was similar. Appearance of microbial threonine in plasma was similar for normal subjects (0.14) and ileostomates (0.17). CONCLUSION: The fate of (15)N from urea and NH(4)Cl differs in terms of endogenous amino acid metabolism, but is similar in relation to microbial protein metabolism. Microbial threonine of normal and ileostomy subjects appears in the blood plasma but the net contribution to the body threonine economy cannot be estimated reliably from the present data.     

稳定性核素在测定大鼠组织蛋白质合成中的应用

目的:研究应用稳定性核素(L-15N亮氨酸)测定大鼠组织蛋白质合成率的方法. 方法:分别测定静脉注射相同剂量L-15N亮氨酸不同时相的大鼠组织15N丰度及不同剂量L-15N亮氨酸的同一时相大鼠组织15N丰度. 结果:大鼠组织中游离及结合氨基酸同位素丰度在注射后半小时内几乎呈线性上升并达高峰,游离氨基酸15N丰度维持4 h后缓慢下降,结合氨基酸15N丰度在半小时至12 h之内基本维持不变;随着注射剂量的增加,大鼠组织蛋白质分数合成率亦增加.当L-15N亮氨酸剂量＞1.0 mmol/kg,分数合成率并不随施加L-15N Leucine剂量的加大而增加. 结论:在进行大鼠组织蛋白质合成率测定时,一次性静脉注射的测量最佳时限为半小时,剂量为1.0 mmol/kg.     

Efficacy of ornithine-alpha-ketoglutarate (OKGA) as a dietary supplement in growing rats

New substrates of potential benefit to critically ill patients receiving traditional nutritional support have been suggested to meet organ or tissue specific needs. The addition of an anabolic stimulus during nutritional support therefore appears to be a reasonable adjunct to augment protein synthesis. The purpose of this investigation was to evaluate the efficacy of the neutral salt ornithine alphaketoglutarate (OKGA) as a dietary supplement to promote growth in young rats by enhancing protein metabolism. A group of 16 male Sprague-Dawley rats (150-170g) were housed in individual metabolic cages and after dark-light cycle adaptation were fed ad libitum an oral liquid diet for 7 days. Half of the animals were given the control diet and the other half was fed a test diet. This isonitrogenous test diet contained the control diet with 2.3% of nitrogen (N) replaced by N from OKGA. Daily weight, food intake and urinary excretions of N, creatinine, urea, orotic acid, polyamines and amino-acids were determined. At the end of 7 days of free-feeding, the rats were sacrificed and blood was collected for free amino-acids. Rats fed the OKGA supplemented diet consumed 16% more diet, retained 11% more nitrogen and gained 15% more weight. The accelerated protein metabolism is reflected in the changes in plasma and urinary free amino-acid levels. Enhanced protein anabolism is evident from the increased urinary excretion of polyamines in the OKGA fed rats. The increased ratio of urinary urea N to total N and the decreased orotic acid excretion in OKGA fed rats suggests thata NH(4)(+) was efficiently diverted through urea cycle. It is concluded that in growing rats, supplementing isonitrogenous diet with OKGA significantly stimulates food intake compared to controls. This results in better weight gain and improvement in protein metabolism.     

Influence of prior dietary protein intake on metabolism, DNA binding and adduct formation of 7,12-dimethylbenz[a]anthracene in isolated rat mammary epithelial cells

These studies were designed to examine the influence of prior dietary protein intakes in rats on the ability of their isolated mammary cells to metabolize 7,12-dimethylbenz[a]anthracene (DMBA). Total metabolism of DMBA increased as dietary protein increased. After 6 h of incubation, water-soluble metabolites made only a minor (less than 12%) contribution to total DMBA metabolism. The binding of DMBA to isolated mammary cell DNA after 6 h of incubation from rats fed 15% dietary protein was 20% higher than binding from cells of rats fed 7.5% dietary protein. The increased binding in mammary epithelial cells from rats fed 15% protein was associated with an increase in the syn-dihydrodiol-epoxide adduct. The syn-dihydrodiol-epoxide:deoxyadenosine adduct was the major contributor to binding. The present studies are consistent with a decrease in carcinogen activation in tissues obtained from animals fed diets limiting in protein.     

The route of administration (enteral or parenteral) affects the conversion of isotopically labeled L-[2-15N]glutamine into citrulline and arginine in humans

BACKGROUND: Glutamine exhibits numerous beneficial effects in experimental and clinical studies. It has been suggested that these effects may be partly mediated by the conversion of glutamine into citrulline and arginine. The intestinal metabolism of glutamine appears to be crucial in this pathway. The present study was designed to establish the effect of the feeding route, enteral or parenteral, on the conversion of exogenously administered glutamine into citrulline and arginine at an organ level in humans, with a focus on gut metabolism. METHODS: Sixteen patients undergoing upper gastrointestinal surgery received an IV or enteral (EN) infusion of L-[2-(15)N]glutamine. Blood was sampled from a radial artery and from the portal and right renal vein. Amino acid concentrations and enrichments were measured, and net fluxes of [(15)N]-labeled substrates across the portal drained viscera (PDV) and kidneys were calculated from arteriovenous differences and plasma flow. RESULTS: Arterial [(15)N]glutamine enrichments were significantly lower during enteral tracer infusion (tracer-to-tracee ratio [labeled vs unlabeled substrate, TTR%] IV: 6.66 +/- 0.35 vs EN: 3.04 +/- 0.45; p < .01), reflecting first-pass intestinal metabolism of glutamine during absorption. Compared with IV administration, enteral administration of the glutamine tracer resulted in a significantly higher intestinal fractional extraction of [(15)N]glutamine (IV: 0.15 +/- 0.03 vs EN: 0.44 +/- 0.08 micromol/kg/h; p < .01). Furthermore, enteral administration of the glutamine tracer resulted in higher arterial enrichments of [(15)N]citrulline (TTR% IV: 5.52 +/- 0.44 vs EN: 8.81 +/- 1.1; p = .02), and both routes of administration generated a significant enrichment of [(15)N]arginine (TTR% IV: 1.43 +/- 0.12 vs EN: 1.68 +/- 0.18). This was accompanied by intestinal release of [(15)N]citrulline across the PDV, which was higher with enteral glutamine (IV: 0.38 +/- 0.07 vs EN: 0.72 +/- 0.11 micromol/kg/h; p = .02), and subsequent [(15)N]arginine release in both groups. CONCLUSIONS: In humans, the gut preferably takes up enterally administered glutamine compared with intravenously provided glutamine. The route of administration, enteral or IV, affects the quantitative conversion of glutamine into citrulline and subsequent renal arginine synthesis in humans.     

不同质蛋白对运动大鼠蛋白质及能量代谢的影响

观察了三种不同质的动、植物蛋白质组成的含蛋白质１７％的饲料对运动大鼠蛋白质及能量代谢的影响。实验取雄性断轧幼鼠３２只，随机等分为Ａ、Ｂ、Ｃ、Ｄ四组。饲料中蛋白质组成：Ａ组为１００％麦蛋白；Ｂ组酪蛋白１０％，麦蛋白９０％；Ｃ及Ｄ组均为酪蛋白４０％，麦蛋白６０％。Ａ、Ｂ、Ｃ组为观察不同质蛋白质对运动大鼠蛋白质及能量代谢的影响，Ｄ组为Ｃ组的安静对照组。观察指杯有体重、氮平衡、骨骼肌氮、血清尿素氮、血糖、血乳酸、肌糖元、肌轧酸脱氢酶、肌ＡＴＰ和肌Ｃａ２＋－ＡＴＰ酶活性。结果表明：１．不同质蛋白影响大鼠蛋白质代谢。Ａ组蛋白质最差、运动后大鼠呈负氮平衡，且血清尿素氮含量较高，肌氮较低，表明蛋白质分解代谢增强。２．不同质蛋白也影响大鼠能量代谢，Ｃ组蛋白质较好，运动时消耗了较多的肌糖原，产生较多的ＡＴＰ；ＬＤＨ和Ｃａ２－ＡＴＰ酶活性较高。３．相同质蛋白的Ｃ、Ｄ组，运动的Ｃ组在能量的产生及酶活性等方面，其数值稍高于安静对照的Ｄ组。４．从蛋白质及能量代谢看，以酪蛋白与麦蛋白４：６为适宜。