四氢生物蝶呤对大鼠低密度脂蛋白氧化修饰的作用及其机制探讨

目的:探讨四氢生物蝶呤(BH4)治疗高脂血症(HL)大鼠对低密度脂蛋白(LDL)氧化修饰作用及其机制。方法:选用8周龄雄性Wistar大鼠54只,随机分为对照组(普通饮食)、高脂饮食组(HL组)和高脂饮食并腹腔注射BH4组(HL+BH4组)(n=18)。于实验前、实验8周和16周时每组各杀死6只大鼠测定血脂和血清BH4水平,测定主动脉血管活性氧(ROS)、脂质过氧化代谢终产物丙二醛(MDA)和LDL氧化修饰水平。结果:至实验8周和16周时,HL组和HL+BH4组血脂水平较对照组均明显升高(P<0.01),但HL组和HL+BH4组之间无明显差异(P>0.05);ROS和MDA明显降低(P<0.01);HL+BH4组较对照组和HL组BH4水平均明显升高(P<0.01);与对照组相比,HL组大鼠主动脉匀浆中BH4含量明显降低(P<0.01),但总喋呤水平(TB=BH4+BH2+B)无明显差异(P>0.05);HL组大鼠血清硫代巴比妥酸反应物(TBARS)生成量随周龄的增加有逐渐升高的趋势,而HL+BH4组大鼠血清TBARS生成量较HL组明显降低(P<0.01)。结论:BH4可以减轻LDL氧化修饰,其机制可能与纠正NOS脱偶联、ROS生成减少及LDL脂质过氧化降低有关。     

自发性高血压大鼠四氢生物碟呤治疗后动脉的结构及力学改变

目的：探讨长期四氢生物喋呤（BH4）治疗对自发性高血压大鼠（SHR）血管形态及血管力学性质的影响;方法：选用4周龄雄性SHR36只,随机分为实验组和对照组,每组18只。实验组每周2次腹腔注射BH420mg／kg,对照组注射等容量生理盐水,于实验第4、16和26周龄时各取6只测量动脉收缩压（SBP）,并使用计算机图像分析的方法分别测量主动脉血管零应力状态张开角、压力-直径关系及肠系膜动脉血管的壁／腔比值。结果：至BH4治疗后的第16和26周龄,SHR的SBP明显降低（P〈0．01）;实验组SHR胸主动脉张开角显著减小（P〈0．01）,压力-直径（P-D）关系曲线上移;实验组肠系膜动脉三级分支血管壁／腔（W／L）值减小（P〈0．05）。结论：BH4可以减弱由于长期高血压所导致的血管肥厚和管腔狭窄,恢复血管弹性。     

姜黄素对抗高脂饮食诱导SD大鼠血脂水平升高及改善血管内皮依赖性舒张功能的研究

目的：观察高脂饮食对SD大鼠血脂水平及胸主动脉环舒张功能的影响及姜黄素对以上改变的影响。方法：健康SD大鼠30只,分高脂饮食组（10只）、正常饮食对照组、高脂饮食＋姜黄素组（10只）,大鼠行适应性饲养1周后分别给予高脂饮食及正常饮食;于实验开始时、10周及实验结束前测各组大鼠体重,20周后取血测定血清血脂浓度,取胸主动脉测定血管环舒张功能。结果：①高脂饮食喂养的大鼠体重明显高于其他各组大鼠,姜黄素可明显对抗高脂饮食导致的体重升高。②与对照组比较,高脂饮食组TC、TG、LDL-C明显升高（P〈0.01和P〈0.05）;③与正常对照组及姜黄素对照组比较,高脂饮食组胸主动脉环的内皮依赖性舒张功能显著减弱（P〈0.05）。结论：①SD大鼠给予高脂饮食后使大鼠血脂水平明显升高,胸主动脉环内皮依赖性舒张功能显著减弱。②姜黄素具有防治高脂饮食导致的血脂升高及改善高脂饮食导致的血管内皮依赖性的舒张功能减退。     

参麦注射液对高脂血症大鼠血脂的调节作用

目的：通过观察参麦注射液对高脂血症模型大鼠的血脂水平和一系列相关生化指标的影响,探讨其对高脂血症模型大鼠血脂的调节作用。方法：30只SPF级雄性SD大鼠用基础饲料适应性喂养1周,随机分为3组（n=10）：对照组,模型对照组,参麦注射液组。对照组用基础饲料喂养,模型对照组和参麦注射液组用高脂饲料喂养,每周测定动物体重一次。参麦注射液组每天给予2次参麦注射液10 ml/kg,连续灌胃45 d。之后测定大鼠血清总胆固醇（TC）、甘油三酯（TG）、高密度脂蛋白（HDL-C）、低密度脂蛋白（LDL-C）、超氧化物歧化酶（SOD）、谷胱甘肽过氧物酶（GSH-Px）、丙二醛（MDA）、脂蛋白酯酶（LPL）和肝酯酶（HL）活性。结果：模型对照组大鼠体重、血清中TC、TG、LDL-C和MDA水平较对照组明显升高（P<0.01）,而HDL-C、SOD、GSH-Px、LPL和HL水平明显降低（P<0.01）。参麦注射液组大鼠体重、血清中TC、TG、LDL-C和MDA水平较模型对照组明显降低（P<0.01）,而HDL-C、SOD、GSH-Px、LPL和HL水平明显升高（P<0.05,P<0.01）。结论：参麦注射液对高脂模型大鼠的血脂具有较明显的调节作用,并具有抗脂质过氧化的作用。     

高脂血症对大鼠心电图的影响及其作用机制

目的：探讨在高脂血症状态下,大鼠心电图的变化情况,及高胆固醇血症对心肌电生理特性影响的机制。方法：将20只Wistar大鼠随机分为空白对照组和高脂饮食组,喂养10周后,检测大鼠的血脂水平、心电图和室颤阈值,并通过全细胞膜片钳记录心室肌细胞的ICa,L;利用组织病理学方法评价对照组及高脂饮食组的大鼠动脉粥样硬化的程度。结果：高脂饮食组的大鼠血脂水平与对照组相比明显增高（P〈0．01）;在高脂饮食组的大鼠动脉血管管壁中,可见广泛分布的粥样硬化斑块。在高脂饮食组的大鼠心电图中,室颤阈值为（4．23±0．12）V,明显低于对照组（12．80±6．34）V,P〈0．05。高脂饮食组大鼠的QTe间期（94±16）ms,与对照组（67±12）ms相比明显延长,P〈0．05。高脂饮食组大鼠的心室肌细胞的ICa,L密度为（12．83±3．28）pA／pF,与对照组（9．21±2．16）pA／pF相比明显高,P〈0．05。结论：高脂饮食后,大鼠的心电图有明显变化,QTe间期延长;高胆固醇血症能明显增加大鼠心肌细胞的ICa,L的,延长复极时程,降低室颤阈值。     

霍山石斛胶囊对高脂血症大鼠血脂和脂质过氧化水平的影响

目的：探讨霍山石斛胶囊（Dendrobium huoshenese capsule,DHC）对高脂血症大鼠的血脂影响及脂质过氧化水平作用。方法：采用高脂饲料建立实验性高脂血症大鼠模型,而后进行低、中、高三种剂量的DHC和阳性对照药血脂康实验性治疗,实验8周后,取大鼠血清、肝脏,检测模型大鼠血清总固醇（Total cholesterol,TC）、甘油三酯（Triglyceride,TG）、低密度脂蛋白胆固醇（Low density lipoprotein cholesterol,LDL—C）、高密度脂蛋白胆固醇（High density lipoprotein cholesterol,HDL—C）含量,并计算动脉粥样硬化指数（Atherosclerosis index,AI）;同时测定血清和肝脏超氧化物歧化酶（Superoxide dismutase,SOD）活性及丙二醛（Malondialdehyde,MDA）含量;并计算肝系数,制备大鼠肝脏石蜡切片观察其病理学变化。结果：与高脂血症模型组相比,DHC中、高剂量组和血脂康组能显著降低高脂血大鼠血清TC、TG、LDL-C,升高HDL—C,表现为AI降低;低剂量的DHC能升高HDL—C,但在降低血清TC、TG、LDL．C和AI上无统计学差异（P〉0．05）;除DHC低剂量组对血清SOD活性升高作用不显著外（P〉0．05）,其他各浓度给药组均能显著升高血清和肝脏SOD活性,降低血清和肝脏MDA含量及肝系数（P〈0．05,P〈0．01）;同时,DHC各给药组还可不同程度降低高脂血症大鼠肝细胞的脂肪变性程度。结论：霍山石斛胶囊能调节血脂代谢异常,增强抗氧化能力,具有防治脂肪肝和抗动脉粥样硬化作用。     

耐力运动对高脂血症小鼠主动脉一氧化氮合酶活性的影响

目的：观察耐力性运动对高脂血症小鼠主动脉一氧化氮合酶（NOS）活性的影响。方法：分别测定正常饮食对照组、正常饮食结合运动组、高脂饮食组、高脂饮食结合运动组小鼠血脂水平及其主动脉固有型NOS（cNOS）和诱导型NOS（iNOS）的活性．结果：高脂饮食降低主动脉cNOS活性,耐力运动可使上述变化逆转;高脂饮食增强主动脉iNOS活性,耐力运动可使iNOS活性略有降低,但无显著性差异。结论：耐力运动可在一定程度上逆转高脂血症引起的cNOS活性降低,这可能属独立于血脂调节作用以外的其它抗动脉硬化机制。     

富硒大豆多肽对高脂致大鼠脂肪肝和抗氧化功能的影响

目的：探讨富硒大豆多肽改善高脂所致脂肪肝大鼠肝抗氧化功能的影响及机制。方法：将40只Wistar大鼠分成4组（n=10）,分别饲喂标准饲料＋水（NC）、标准饲料＋富硒大豆多肽液（SeN）、高脂饲料＋水（HC）、高脂饲料＋富硒大豆多肽液（SeH）,10周后处死,用苏丹Ⅲ染色肝脏组织切片观察脂肪变性程度,免疫组织化学方法测定肝组织葡萄糖调节蛋白78（GRP78）表达情况,并分析其肝功能、血脂及血清和肝匀浆中谷胱甘肽过氧化物酶（GSH-Px）、超氧化物歧化酶（SOD）活性和丙二醛（MDA）含量的变化情况。结果：HC组在血清TC、TG水平、肝脏脂肪化程度、GRP78表达情况都明显高于NC、SeN、SeH组（P〈0.01）。SeH组血清和肝组织中MDA含量较HC组降低（P〈0.01）,GSH-Px、SOD活性升高。NC和SeN两组各项指标之间无明显差异。结论：富硒大豆多肽能有效提高脂肪肝大鼠肝内抗氧化酶活性,抑制脂质过氧化反应,降低肝组织内GRP78表达。     

NP c 1L l 在高脂血症和动脉粥样硬化中的表达分析

目的：研究NPC1L1（Niemann-Pick C1 Like 1）mRNA在单纯高脂血症大鼠和动脉粥样硬化大鼠小肠组织中的表达与差异,探讨其与脂质代谢和动脉粥样硬化之间的关系。方法：通过半定量RT-PCR方法分别检测正常普食组、单纯高脂饲养组和动脉粥样大鼠组小肠组织中NPC1L1 mRNA的表达差异。结果：三个组别大鼠小肠组织中均存在NPC1L2 mRNA,单纯高脂饮食和动脉粥样大鼠小肠组织中NPC1L1 mRNA表达明显高于正常对照大鼠（P〈0．01）;单纯高脂饮食和动脉粥样大鼠小肠组织中NPC1L1 mRNA表达之间无明显差异（P〉0．05）。结论：血脂代谢紊乱与小肠组织中NPC1L1的高表达有关,NPC1L1可能参与了血脂紊乱的病理生理过程;NPC1L1与促成动脉粥样硬化的发生无明显相关性。     

绞股蓝总皂甙对实验性高脂血症大鼠血脂和脂质过氧化水平的影响

目的：研究绞股蓝总皂甙对实验性高脂血症大鼠血脂的调节机制并探索其抗脂质过氧化的机理。方法：用高脂饲料喂饲大鼠6周,复制成高脂血症模型,而后进行4周高、低两种剂量的绞股蓝和阳性对照药血脂康实验性治疗。给药4周后处死动物,比较血清总胆固醇及甘油三酯含量、血清高密度脂蛋白胆固醇和低密度脂蛋白胆固醇含量,同时测定血清SOD、CAT和MDA的浓度。结果：高、低剂量的绞股蓝总皂甙均可显著降低大鼠血清低密度脂蛋白胆固醇、总胆固醇、甘油三脂浓度,提高高密度脂蛋白胆固醇水平 绞股蓝总皂甙组大鼠血清超氧化物歧化酶、谷胱甘肽过氧化物酶及过氧化氢酶显著升高,脂质过氧化产物水平显著降低。结论：绞股蓝总皂甙可治疗高血脂症大鼠血脂异常并有较明显的抗脂质过氧化作用。     

Enhanced Expressions of Arginine Vasopressin (Avp) in the Hypothalamic Paraventricular and Supraoptic Nuclei of Type 2 Diabetic Rats

Arginine vasopressin (AVP) is known to a neuropeptide that plays important roles in water conservation, sodium homeostasis, and in the regulation of serum osmolality. Several studies have reported that the elevated AVP level is related with diabetes mellitus as an acute or chronic stressor using type 1 diabetes mellitus animal models. However, it is unclear as to how the immunoreactivity and protein level of AVP in the brain is regulated in animal models of type 2 diabetes mellitus. In the present study, Zucker diabetic fatty (ZDF) rats were employed as a type 2 diabetes mellitus model and were compared with Zucker lean control (ZLC) rats with respect to AVP protein expression. Furthermore, in order to verify the regulation of AVP expression before and after the onset of diabetes mellitus, pre-diabetic rats (4 week-old) and obese-diabetic rats (12 week-old) were used. Blood glucose levels and water consumption were also measured and the results showed significantly high in 12 week-old ZDF than any other groups. AVP expression levels in the paraventricular nucleus and supraoptic nucleus were found to be significantly higher in 12 week-old ZDF rats than in 12 week-old ZLC rats and than in 4 week-old rats by immunostaining and western blotting. Enhanced expression of AVP in these animals may be associated with type 2 diabetes mellitus. Special issue article in honor of George Fink.     

Antihypertensive therapy increases tetrahydrobiopterin levels and NO/cGMP signaling in small arteries of angiotensin II-infused hypertensive rats

We previously reported that small mesenteric arteries from hypertensive rats have increased NOS-derived H(2)O(2) and reduced NO/cGMP signaling. We hypothesized that antihypertensive therapy lowers blood pressure through a tetrahydrobiopterin (BH(4))-dependent mechanism restoring NO/cGMP signaling and endothelial NOS (NOS3; eNOS) phosphorylation in small arteries. To test this hypothesis, small mesenteric arteries from normotensive rats (NORM), angiotensin II-infused rats (ANG), ANG rats with triple therapy (reserperine, hydrochlorothiazide, and hydralazine), or ANG rats with oral BH(4) therapy were studied. Both triple therapy and oral BH(4) therapy attenuated the rise in systolic blood pressure in ANG rats and restored NO/cGMP signaling in small arteries similarly. Triple therapy significantly increased vascular BH(4) levels and BH(4)-to-BH(2) ratio similar to ANG rats with BH(4) supplementation. Furthermore, triple therapy (but not oral BH(4) therapy) significantly increased GTP cyclohydrolase I (GTPCH I) activity in small arteries without a change in expression. NOS3 phosphorylation at Ser1177 was reduced in small arteries from ANG compared with NORM, while NOS3 phosphorylation at Ser633 and Thr495 were similar in ANG and NORM. NOS3 phosphorylation at Ser1177 was restored with triple therapy or oral BH(4) in ANG rats. In conclusion, antihypertensive therapy regulates NO/cGMP signaling in small arteries through increasing BH(4) levels and NOS3 phosphorylation at Ser1177.     

Tetrahydrobiopterin improves vascular endothelial function in ovariectomized rats

The goal of the present study is to investigate the role of tetrahydrobiopterin (BH4) in the vascular response in ovariectomized rats. Rats were randomly assigned to two groups: (1) sham group: sham-operated female rats, and (2) Ovx group: rats were ovariectomized. Our results have shown that the plasma 17 beta-estradiol levels in the Ovx group at the end of the experiment were significantly lower than in the sham group. Vasoreactivity assessed with intact aortic rings indicated that the phenylephrine-induced vasocontractile response to aortic rings from the Ovx group was greater than that of the sham group. In contrast, the vasodilator responses to acetylcholine and L-arginine (L-Arg) in the sham group were significantly greater than in the Ovx group. Differences in vasoreactivity in denuded aorta between the two groups were not noted. Moreover, exogenous BH4 significantly restored L-Arg-induced vasodilator responses in the Ovx group. However, this improvement effect was not found in the sham group. In addition, there were significant increases in superoxide anion production in aortic tissue and significant decreases in plasma nitric oxide levels in the Ovx group. Furthermore, BH4 contents in the aorta in the Ovx group were significantly decreased compared with the sham group. In conclusion, the present study demonstrates that the impairment of vascular reactivity was found in the ovariectomized rats. The possible mechanism of this defect may have resulted from the deficiency of available BH4. Thus, this study may provide a novel therapeutic strategy for the treatment of postmenopausal cardiovascular disorders.     

Mechanical effects of muscle contraction do not blunt sympathetic vasoconstriction in humans

Sympathetic vasoconstrictor responses are blunted in the vascular beds of contracting muscle (functional sympatholysis), but the mechanism(s) have been difficult to elucidate. We tested the hypothesis that the mechanical effects of muscle contraction blunt sympathetic vasoconstriction in human muscle. We measured forearm blood flow (Doppler ultrasound) and calculated the reductions in forearm vascular conductance (FVC) in response to reflex increases in sympathetic activity evoked via lower body negative pressure (LBNP). In protocol 1, eight young adults were studied under control resting conditions and during simulated muscle contractions using rhythmic forearm cuff inflations (20 inflations/min) with cuff pressures of 50 and 100 mmHg with the arm below heart level (BH), as well as 100 mmHg with the arm at heart level (HL). Forearm vasoconstrictor responses (%DeltaFVC) during LBNP were -26 +/- 2% during control conditions and were not blunted by simulated contractions (range = -31 +/- 3% to -43 +/- 6%). In protocol 2, eight subjects were studied under control conditions and during rhythmic handgrip exercise (20 contractions/min) using workloads of 15% maximum voluntary contraction (MVC) at HL and BH (similar metabolic demand, greater mechanical muscle pump effect for the latter) and 5% MVC BH alone and in combination with superimposed forearm compressions of 100 mmHg (similar metabolic demand, greater mechanical component of contractions for the latter). The forearm vasoconstrictor responses during LBNP were blunted during 15% MVC exercise with the arm at HL (-1 +/- 3%) and BH (-2 +/- 3%) compared with control (-25 +/- 3%; both P < 0.005) but were intact during both 5% MVC alone (-24 +/- 4%) and with superimposed compressions (-23 +/- 4%). We conclude that mechanical effects of contraction per se do not cause functional sympatholysis in the human forearm and that this phenomenon appears to be coupled with the metabolic demand of contracting skeletal muscle.     

Co-induction of nitric oxide and tetrahydrobiopterin synthesis in the myocardium in vivo

Induction of the inducible isoform of nitric oxide (NO) synthase (iNOS) in the myocardium is implicated as a mechanism in the development of cardiac depression in immune activated states associated with an enhanced release of cytokines, such as septic shock. We evaluated the in vivo synthesis of NO and tetrahydrobiopterin (BH4), a cofactor of NOS, in the heart tissue using a model of LPS injection in rats (LPS: 10 mg/kg, i.v.). In control rats, iNOS activity or iNOS mRNA in the heart was negligible. Three hours after LPS administration, a marked induction of iNOS mRNA and activity was observed in the heart. A significant increase in BH4 content and GTP cyclohydrolase mRNA abundance was also observed in the heart from LPS-treated rats. Our results demonstrate induction of NO synthesis and parallel increase in BH4 concentration in the heart of rats after LPS treatment in vivo and may provide molecular evidence responsible for the increased production of BH4 which may up-regulate iNOS activity in the heart in vivo. (Mol Cell Biochem 166: 177-181, 1997)     

Selective inhibitory effects of hybrid liposomes on the growth of HIV type 1-infected cells in vitro

A good correlation between fifty-percent inhibitory concentration (IC(50)) of hybrid liposomes (HL) composed of dimyristoylphosphatidylcholine and polyoxyethylene(n) dodecyl ether on the growth of MOLT-4/IIIB cells (MOLT-4 cells chronically infected with human immunodeficiency virus (HIV)) and the membrane fluidity of HL was obtained. Furthermore, the huge enhancement of virus production was observed in the latently HIV-infected (J(22)-HL-60) cells after the treatment with HL.     

Diminished expression of dihydropteridine reductase is a potent biomarker for hypertensive vessels

To identify the new targets for hypertension, we analyzed the protein expression profiles of aortic smooth muscle in spontaneously hypertensive rats (SHR) of various ages during the development of hypertension, as well as in age‐matched normotensive Wistar–Kyoto (WKY) rats, using a proteomic analysis. The expressions of seven proteins were altered in SHR compared with WKY rats. Of these proteins, NADH dehydrogenase 1α, GSTω1, peroxi‐redoxin I and transgelin were upregulated in SHR compared with WKY rats. On the other hand, the expression of HSP27 and Ran protein decreased in SHR. The diminution of dihydrobiopterin reductase, an enzyme located in the regeneration pathways of tetrahydrobiopterin (BH4), was also prominent in SHR. The results from a PCR analysis revealed that the expression of BH4 biosynthesis enzymes – GTP cyclohydrolase‐1 and sepiapterin reductase – decreased and increased, respectively, in SHR compared with WKY rats. The level of BH4 was less in aortic strips from SHR than from WKY rats. Moreover, treatment with BH4 inhibited aortic smooth muscle contraction induced by serotonin. These results suggest that the deficiency in BH4 regeneration produced by diminished dihydrobiopterin reductase expression is involved in vascular disorders in hypertensive rats.     

Tetrahydrobiopterin, a cofactor for NOS, improves endothelial dysfunction during chronic alcohol consumption

We sought to investigate mechanisms that may account for impaired nitric oxide synthase (NOS)-dependent dilatation of cerebral arterioles during alcohol consumption. Our goals were to examine 1) the effect of exogenous application of a cofactor for NOS, i.e., tetrahydrobiopterin (BH4) on the reactivity of pial arterioles during alcohol consumption; and 2) endothelial NOS (eNOS) protein in nonalcohol-fed and alcohol-fed rats. Sprague-Dawley rats were fed liquid diets with or without alcohol for 2-3 mo. We measured in vivo diameter of pial arterioles in response to NOS-dependent agonists (ACh and ADP) and a NOS-independent agonist (nitroglycerin) before and during application of BH4. Blood vessels were then harvested for Western blot analysis of eNOS protein. In nonalcohol-fed rats, ACh and ADP produced vasodilatation, which was impaired in alcohol-fed rats. Vasodilatation to nitroglycerin was similar in both groups of rats. Application of BH4 did not alter vasodilatation in nonalcohol-fed rats but improved impaired vasodilatation in alcohol-fed rats. Also, eNOS protein in cerebral cortex microvessels, the basilar artery, and aorta was not different between nonalcohol-fed and alcohol-fed rats. Thus impaired NOS-dependent vasodilatation during alcohol consumption does not appear to be related to an alteration in eNOS protein but may be related to a deficiency and/or alteration in the utilization of BH4.