一氧化氮对心肌的抑制性保护作用

内皮型与神经型一氧化氮合酶(eNOS,nNOS)在心肌细胞内持续表达,而细胞应激可引起诱导型NOS(iNOS)表达.心肌细胞结构型eNOS与nNOS源性NO,在生理条件下对心肌主要发挥4方面的抑制作用:减缓心肌细胞搏动频率,轻度抑制心肌细胞收缩功能,加速心肌细胞舒张并增加顺应性,以及轻度抑制线粒体电子传递而增强氧利用效...     

银杏叶提取物对糖尿病大鼠心肌损伤的防护作用

目的:研究银杏叶提取物(EGb)对糖尿病大鼠心肌的防护作用.方法:用光镜和透射电镜观察EGb对糖尿病大鼠心肌的形态学改变,并测定心肌组织内超氧化物歧化酶(SOD)、一氧化氮合酶(NOS)、结构型一氧化氮合酶(cNOS)、诱导型一氧化氮合酶(iNOS)的活性及一氧化氮(NO)、丙二醛(MDA)的含量.结果:糖尿病大鼠心肌光镜下主要表现为心肌细胞空泡变性及心肌纤维局灶性溶解;电镜下主要表现为心肌线粒体肿胀,嵴变短,肌原纤维溶解;SOD活性下降,NOS、iNOS活性及MDA、NO含量增高.EGb治疗组病变明显减轻,EGb治疗组心肌组织内SOD活性明显高于糖尿病组,NOS、iNOS活性及MDA、NO含量低于糖尿病组.结论:EGb可能通过抗脂质过氧化作用和降低NO水平而对糖尿病心肌产生保护作用.     

封面故事

<正>生物体内存在着复杂的一氧化氮合酶(nitric oxide synthase,NOS)活性调节机制以精确调控一氧化氮的生成。在神经系统中,一氧化氮主要由神经型一氧化氮合酶(neuronal nitric oxide synthase,nNOS)催化生成     

HIF-NOS信号通路对哺乳动物卵巢NO依赖性功能的调控作用

一氧化氮(NO)作为气体明星分子和信号分子,在哺乳动物体内不同的生理调节过程中具有非常重要的作用,尤其是哺乳动物卵巢功能的调控.一氧化氮合酶(NOS)是NO合成的限速酶,是调节NO合成的关键环节,也是NO依赖性功能调控的重要环节.因此,调节NOS转录/合成的信号通路对哺乳动物卵巢NO依赖性功能具有至关重要的调控作用.最近的研究发现,缺氧诱导因子(HIF)作为转录因子,参与许多与缺氧相关靶基因的转录调控,如NOS和血管内皮生长因子(VEGF)等.本文一方面描述了NO合成及其调控的分子机制,另一方面阐明了HIF作为转录因子对NOS的转录调控,从而揭示HIF在NO依赖性卵巢功能调控中的重要作用,同时为进一步研究哺乳动物卵巢功能的调控提供新的研究方向和理论基础.     

绞股蓝总黄酮对低氧/复氧心肌细胞Ca2+及NOS-NO系统的作用

目的:探讨纹股蓝总黄酮对培养心肌细胞低氧/复氧报伤的Ca2+超载、一氧化氮合酶一氧化氮(NOS-NO)系统的影响.方法:培养心肌细胞,建立低氧/复氧损伤模型;荧光分光光度法测定心肌细胞内Ca2+,比色法测心肌细胞培养上清液NO含量、细胞匀浆NOS活性.结果:绞股蓝总黄酮降低低氧/复氧心肌细胞内Ca2+、T-NOS、iN...     

尾加压素对新生大鼠心肌细胞一氧化氮合成的影响

应用半定量逆转录－多聚酶链反应法,观察尾加压素（urotensin Ⅱ,UⅡ）对培养的新生SD大鼠心肌细胞内皮型一氧化氮合酶（endothelial nitric oxide synthase,eNOS)mRNA表达的影响,并测定UⅡ对心肌细胞内一氧化氮合酶（nitric oxide synthase,NOS)活性和一氧化氮（nitric oxide,NO)释放的影响。结果显示：UⅡ抑制培养的新生大鼠心肌细胞eNOS mRNA表达、抑制NOS的活性及NO释放;0.1μmol/L浓度的UⅡ呈时间依赖性抑制心肌细胞NOS的活性及NO生成。上述实验结果提示UⅡ的心血管作用可能与NO合成系统有关。     

一氧化氮合酶的遗传、生理研究进展

一氧化氮具有广泛的生理功能,哺乳动物体内的NO是由NO合酶(NOS)氧化L-精氨酸而合成的,合成后的NO迅速跨膜扩散释放,NO合成失调能介导多种疾病。催化NO生物合成的NOS有三种亚型:神经元型NOS(nNOS)、内皮型NOS(eNOS)和诱导型NOS(iNOS),目前,人的三型NOS已纯化并且已分子克隆成功,对一氧化氮合酶的遗传研究确认了NOS家族的基因结构和染色体定位。     

两种败血症休克模型大鼠心肌细胞一氧化氮合酶活性的改变

目的：观察两种败血症休克模型大鼠的血流动力学及心肌细胞一氧化氮合酶活性变化的异同,探讨一氧化氮合酶参与败血症休克性心肌抑制的机制。方法：采用注射脂多糖（LPS）诱导及盲肠结扎穿孔（CLP）致腹膜炎诱导败血症休克模型,测定血流动力学指标以及心肌细胞胞浆一氧化氮合酶（NOS）活性。结果：①CLP模型大鼠的血流动力学指标随时间呈先上升后下降的趋势,LPS模型直接表现为类似于CLP模型晚期的动力学状态。在使用NOS抑制剂N-硝基-L精氨酸甲酯（L-NAME）后,CLP模型晚期及LPS模型的心室动力学指标均有明显改善。②CLP模型大鼠心肌细胞胞浆NOS活性在败血症中期达到最大。与假手术组相比,LPS模型、CLP模型晚期心肌细胞胞浆NOS活性均有明显增加,但是LPS模型与CLP模型晚期两组之间无明显差异。③使用L-NAME后,CLP晚期组与LPS组亚硝基及硝基化合物生成量均明显降低（P〈0.01）。其中,LPS组与CLP晚期组相比,前者固定表达型NOS生成亚硝基及硝基化合物生成量明显高于后者（P〈0．01）。结论：在LPS与CLP诱导的败血症休克模型中,心肌NOS是引起心室动力学变化的主要因素;在两种模型,心肌NOS亚型的表达不同,在LPS模型中主要为iNOS,而在CLP模型中则可能是cNOS和iNOS共同发挥作用。     

妊娠中晚期接触可卡因对子代NOS分布影响的免疫组织化学研究

目的：建立妊娠中晚期接触可卡因的小鼠动物模型,研究可卡因对子代脑内一氧化氮合酶（nitric oxide sythase,NOS）分布和含量的影响,同时探讨这种影响的意义。方法：采用免疫组织化学结合图像分析技术观察纹体内与海马内NOS的分布与相对含量。结果：实验结果表明,妊娠中晚期接触可卡因导致子代纹状体神经元性一氧化氮合酶（neural NOS,nNOS）与海马CA1区与CA3区内皮细胞源性一氧化氮合酶（endothelial NOS,eNOS）免疫染色增强,相对含量增多。结论：妊娠中晚期接触可卡因可引起子代脑内NOS发生改变,这种变化是可卡因引起的机体神经毒性反应,还是机体对可卡因毒性反应的代偿机制,还有待于进一步研究。     

一氧化氮合酶的若干研究进展

一氧化氮合酶(NOS)是一氧化氮(NO)生物学与医学研究的重要内容.近年来,对NOS酶本质及其生化与分子生物学特性甚至某些分子遗传学方面的认识都在迅速发展和深化.研究表明,干预NOS-NO途径的某些环节,如酶激活、NO合成、释放与转运甚至有关酶的编码基因及其表达,将为某些临床问题的解决提供新的思路和手段．     

氨甲酰胆碱通过M2胆碱能受体对大鼠心肌细胞发挥正性肌力作用

为研究氨甲酰胆碱（carbachol,CCh）对大鼠心肌细胞的正性肌力作用机制,利用电压钳方法观察CCh对急性分离的单个大鼠心肌细胞L-型钙电流（足扎）和钠,钙交换电流（INa/Ca）的影响。细胞负载Fura-2／AM后,用离子成像系统测定场刺激下单个大鼠心肌细胞的钙瞬变和细胞缩短。结果表明,100ILmol／LCCh使正向INa/Ca从（1．18±0．57）pA／pF增加到（1．65±0．52）pA/pF（P〈O．01）,反向,INa/Ca从（1．11±0．49）pA/pF增加到（1．53±0．52）pA/pF（P〈O．01）,但不影响ICa,L。阿托品（非选择性M胆碱受体拮抗剂）和methoctramine（选择性M2胆碱受体拮抗剂）可阻断这种增加作用。100μmol／LCCh使钙瞬变从对照组的203．8±50．0增加到234．8±64.3,使细胞缩短从对照组的（3．00±0．67）μm增加到（3．55±1．21）μm。KB-R7943（选择性反向INa/Ca抑制剂）不影响钙瞬变和细胞缩短的基础水平,却完全阻断CCh引起的钙瞬变和细胞缩短的增加。尼卡地平（ICa,L抑制剂）抑制钙瞬变和细胞缩短。CCh在尼卡地平存在下仍可增加钙瞬变和细胞缩短值,提示其正性肌力作用是通过刺激钠,钙交换实现的。CCh不改变钙敏感性。阿托品和methoctramine阻断CCh的这种激动作用,说明CCh的正性肌力作用是通过M2受体实现的。以上结果提示,CCh对大鼠心肌细胞有正性肌力作用,这种作用是通过激动反向钠／钙交换实现,由M2受体介导。     

腺苷抗豚鼠室性心律失常的电生理研究

实验用全细胞膜片钳技术在单个豚鼠心室肌细胞上研究了腺苷 (Ado)对正常及异丙肾上腺素 (Iso)致豚鼠心室肌细胞动作电位、迟后除极 (DAD)、L 型钙电流 (ICa.L)和短暂内向电流 (Iti)的作用。结果表明 :(1)Ado在2 0～ 10 0 μmol/L时对豚鼠心室肌细胞动作电位和ICa .L无明显直接作用 ,但却可明显降低Iso所致的动作电位时程(APD)延长和ICa .L峰值增大 ,Iso (10nmol/L)使细胞APD50 从 3 40± 2 1ms延长到 486± 2 8ms (P <0 0 1) ,APD90从 3 61± 17ms延长至 5 0 1± 2 9ms (P <0 0 1) ;ICa .L峰值从 - 6 5 3± 1 4pA/pF增大到 - 18 2 8± 2 4pA/pF (P <0 0 1) ,电流电压曲线明显左移和下移 ;Ado (5 0 μmol/L)使APD50 和APD90 降至 40 3± 19ms和 419± 2 6ms ,但并不影响动作电位其它参数 ,使ICa.L峰值降低至 - 10 2± 1 5pA/pF (P <0 0 1)。 (2 )Iso (3 0nmol/L)可诱发心室肌细胞产生DADs,其发生率为 10 0 % ;Ado (5 0 μmol/L)可完全抑制Iso引发DADs;细胞经 - 40～ +2 0mV、时程 2s的除极电压 ,Iso (3 0nmol/L)诱导出Iti,其发生率为 10 0 % ;Ado (5 0 μmol/L)可明显抑制Iso致Iti的发生 ,其发生率降为 14 3 %。研究结果提示 ,Ado对豚鼠心室肌细胞动作电位和ICa.L无明显直接作用 ,但却可显著降低Is     

Involvement of veratridine-induced increase of reverse Na(+)/Ca(2+) exchange current in intracellular Ca(2+) overload and extension of action potential duration in rabbit ventricular myocytes

The objectives of this study were to investigate the effects of veratridine (VER) on persistent sodium current (I(Na.P)), Na(+)/Ca(2+) exchange current (I(NCX)), calcium transients and the action potential (AP) in rabbit ventricular myocytes, and to explore the mechanism in intracellular calcium overload and myocardial contraction enhancement by using whole-cell patch clamp recording technique, visual motion edge detection system, intracellular calcium measurement system and multi-channel physiological signal acquisition and processing system. The results showed that I(Na.P) and reverse I(NCX) in ventricular myocytes were obviously increased after giving 10, 20 μmol/L VER, with the current density of I(Na.P) increasing from (-0.22 ± 0.12) to (-0.61 ± 0.13) and (-2.15 ± 0.14) pA/pF (P < 0.01, n = 10) at -20 mV, and that of reverse I(NCX) increasing from (1.62 ± 0.12) to (2.19 ± 0.09) and (2.58 ± 0.11) pA/pF (P < 0.05, n = 10) at +50 mV. After adding 4 μmol/L tetrodotoxin (TTX), current density of I(Na.P) and reverse I(NCX) returned to (-0.07 ± 0.14) and (1.69 ± 0.15) pA/pF (P < 0.05, n = 10). Another specific blocker of I(Na.P), ranolazine (RAN), could obviously inhibit VER-increased I(Na.P) and reverse I(NCX). After giving 2.5 μmol/L VER, the maximal contraction rate of ventricular myocytes increased from (-0.91 ± 0.29) to (-1.53 ± 0.29) μm/s (P < 0.01, n = 7), the amplitude of contraction increased from (0.10 ± 0.04) to (0.16 ± 0.04) μm (P < 0.05, n = 7), and the baseline of calcium transients (diastolic calcium concentration) increased from (1.21 ± 0.08) to (1.37 ± 0.12) (P < 0.05, n = 7). After adding 2 μmol/L TTX, the maximal contraction rate and amplitude of ventricular myocytes decreased to (-0.86 ± 0.24) μm/s and (0.09 ± 0.03) μm (P < 0.01, n = 7) respectively. And the baseline of calcium transients reduced to (1.17 ± 0.09) (P < 0.05, n = 7). VER (20 μmol/L) could extend action potential duration at 50% repolarization (APD(50)) and at 90% repolarization (APD(90)) in ventricular myocytes from (123.18 ± 23.70) to (271.90 ± 32.81) and from (146.94 ± 24.15) to (429.79 ± 32.04) ms (P < 0.01, n = 6) respectively. Early afterdepolarizations (EADs) appeared in 3 out of the 6 cases. After adding 4 μmol/L TTX, APD(50) and APD(90) were reduced to (99.07 ± 22.81) and (163.84 ± 26.06) ms (P < 0.01, n = 6) respectively, and EADs disappeared accordingly in 3 cases. It could be suggested that: (1) As a specific agonist of the I(Na.P), VER could result in I(Na.P) increase and intracellular Na(+) overload, and subsequently intracellular Ca(2+) overload with the increase of reverse I(NCX). (2) The VER-increased I(Na.P) could further extend the action potential duration (APD) and induce EADs. (3) TTX could restrain the abnormal VER-induced changes of the above-mentioned indexes, indicating that these abnormal changes were caused by the increase of I(Na.P). Based on this study, it is concluded that as the I(Na.P) agonist, VER can enhance reverse I(NCX) by increasing I(Na.P), leading to intracellular Ca(2+) overload and APD abnormal extension.     

血清Hcy、FA、VitB12水平及H.pylori感染与脑梗死的相关性研究

目的：探讨脑梗死（cerebral infarction,CI）患者血清同型半胱氨酸（homocysteine,Hcy）、叶酸（folate,FA）、维生素B12（Vitamin B12,VitBl2）水平及幽门螺杆菌（H_pylori）感染与脑梗死的关系,为预防和治疗脑梗死提供参考依据。方法：选择本科收治的132例脑梗死患者和同期81例健康对照者为研究对象,检测和比较其血清同型半胱氨酸（Hey）、叶酸（FA）、VitB12水平及HP-IgG抗体。结果：（1）脑梗死患者H．pylori的感染率为50．76％,显著高于健康对照组（35．80％）（X2=0．54,P〈0．05）;（2）脑梗死患者血清Hey[（20．02±8．84）μmol／L]和FA水平[（14．47±6．38）ng／mL）]与健康对照组[（12．36±4．97）μmol／L,（16．82±11．43）ng／mL）]比较,均具有显著差异（P〈0．01,P〈0．01）;而VitB12水平与健康对照组比较无统计学意义（P〉0．05）;（3）脑梗死患者中,HP-IgG阳性的患者Hey水平[（24．20±8．81）μmol／L]明显高于HP-IgG阴性的患者[（15．71±6．53）μmol／L]（P〈0．01）,血清FA水平[（14．59±7．54）ng／mL）]明显低于于HP-IgG阴性的患者[（14．43±4．98）ng／mL]（P〈0．05）,而两组之间VitBl2水平比较无明显差异（P〉0．05）;HP—IgG阳性的脑梗死患者Hey水平[（24．20±8．81）bLmol／L]与HP—IgG阳性的健康对照组[（13．25±5．24）μmol／L]相比,差异显著（P〈0．05）,FA,VitB12水平低于健康对照组,但并无显著差异（P〉0．05）.结论：脑梗死患者H．pylori的感染率高于健康人群;H．pylori感染可能影响脑梗死患者Hey的代谢,导致Hey水平升高,促进了脑梗死的发生和发展。     

The COX-2 inhibitor Celecoxib enhances the sensitivity of KB/VCR oral cancer cell lines to Vincristine by down-regulating P-glycoprotein expression and function

Previous studies have indicated that long-term chemotherapy decreases the sensitivity of oral cancer cells to chemotherapeutics while simultaneously increasing resistance to these drugs. COX-2 inhibitors are known to enhance the toxic action of anti-tumor drugs against cancer cells. Using the MTT method, we investigated the influence of the COX-2 selective inhibitor Celecoxib on the proliferation of KB/VCR oral cancer cell lines and analyzed the effect of Celecoxib on the regulation of P-glycoprotein (P-gp) expression and function. Western blot analysis was employed to detect the expression of P-gp, and flow cytometry was used to evaluate P-gp function by detecting the accumulation of the active P-gp functional fluorescence substrate within KB/VCR cells. The results revealed that a low dose of Celecoxib (10 μmol/L) showed no growth inhibitory effects on KB/VCR cell lines. When the concentration of Celecoxib was greater than or equal to 20 μmol/L, the inhibitory effect on KB/VCR cells was significantly enhanced in a time- and dose-dependent manner. The lower dose of Celecoxib (10 μmol/L) significantly enhanced the toxicity of Vincristine (VCR) against KB/VCR cell lines. After the application of Celecoxib plus VCR (10 μmol/L+1.5μmol/L, respectively) treatment for 24, 48 or 72 h, the growth inhibition rates of KB/KBV cells were 37.82 ± 1.60%, 47.84 ± 1.29% and 54.43 ± 2.35%, respectively, which were significantly higher than the rates in the cells treated only with Celecoxib (10 μmol/L) or VCR (1.5 μmol/L) (all P<0.01). P-gp expression levels in KB/KBV cells treated with Celecoxib plus VCR (10 μmol/L+1.5 μmol/L, respectively) were markedly lower than the levels in control cells and those treated with VCR (1.5 μmol/L) (all P<0.01). In addition, the intensity of Rho123 fluorescence of KB/KBV cells in cells treated with Celecoxib plus VCR (10 μmol/L+1.5 μmol/L, respectively) or Celecoxib alone (10 μmol/L) was significantly higher than the intensity observed in control cells and those treated with VCR alone (1.5 μmol/L) (all P<0.01). The underlying mechanism of these phenomena is likely correlated with the down-regulation of the expression and function of P-gp due to Celecoxib, thereby increasing the amount of VCR accumulated in KB/VCR cells.     

Adenosine A2A receptor activation attenuates tubuloglomerular feedback responses by stimulation of endothelial nitric oxide synthase

Adenosine A(2) receptors have been suggested to modulate tubuloglomerular feedback (TGF) responses by counteracting adenosine A(1) receptor-mediated vasoconstriction, but the mechanisms are unclear. We tested the hypothesis that A(2A) receptor activation blunts TGF by release of nitric oxide in the juxtaglomerular apparatus (JGA). Maximal TGF responses were measured in male Sprague-Dawley rats as changes in proximal stop-flow pressure (ΔP(SF)) in response to increased perfusion of the loop of Henle (0 to 40 nl/min) with artificial tubular fluid (ATF). The maximal TGF response was studied after 5 min intratubular perfusion (10 nl/min) with ATF or ATF + A(2A) receptor agonist (CGS-21680; 10(-7) mol/l). The interaction with nitric oxide synthase (NOS) isoforms was tested by perfusion with a nonselective NOS inhibitor [N(ω)-nitro-L-arginine methyl ester hydrochloride (L-NAME); 10(-3) mol/l] or a selective neuronal NOS (nNOS) inhibitor [N(ω)-propyl-L-arginine (L-NPA); 10(-6) mol/l] alone, and with the A(2A) agonist. Blood pressure, urine flow, and P(SF) at 0 nl/min were similar among the groups. The maximal TGF response (ΔP(SF)) with ATF alone (12.3 ± 0.6 mmHg) was attenuated by selective A(2A) stimulation (9.5 ± 0.4 mmHg). L-NAME enhanced maximal TGF responses (18.9 ± 0.4 mmHg) significantly more than L-NPA (15.2 ± 0.7 mmHg). Stimulation of A(2A) receptors did not influence maximal TGF response during nonselective NOS inhibition (19.0 ± 0.4) but attenuated responses during nNOS inhibition (10.3 ± 0.4 mmHg). In conclusion, adenosine A(2A) receptor activation attenuated TGF responses by stimulation of endothelial NOS (eNOS), presumably in the afferent arteriole. Moreover, NO derived from both eNOS and nNOS in the JGA may blunt TGF responses.     

Mepivacaine-induced contraction is attenuated by endothelial nitric oxide release in isolated rat aorta

Mepivacaine is an aminoamide-linked local anesthetic with an intermediate duration that intrinsically produces vasoconstriction both in vivo and in vitro. The aims of this in-vitro study were to examine the direct effect of mepivacaine in isolated rat aortic rings and to determine the associated cellular mechanism with a particular focus on endothelium-derived vasodilators, which modulate vascular tone. In the aortic rings with or without endothelium, cumulative mepivacaine concentration-response curves were generated in the presence or absence of the following antagonists: N(ω)-nitro-L-arginine methyl ester [L-NAME], indomethacin, fluconazole, methylene blue, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one [ODQ], verapamil, and calcium-free Krebs solution. Mepivacaine produced vasoconstriction at low concentrations (1 × 10(-3) and 3 × 10(-3) mol/L) followed by vasodilation at a high concentration (1 × 10(-2) mol/L). The mepivacaine-induced contraction was higher in endothelium-denuded aortae than in endothelium-intact aortae. Pretreatment with L-NAME, ODQ, and methylene blue enhanced mepivacaine-induced contraction in the endothelium-intact rings, whereas fluconazole had no effect. Indomethacin slightly attenuated mepivacaine-induced contraction, whereas verapamil and calcium-free Krebs solution more strongly attenuated this contraction. The vasoconstriction induced by mepivacaine is attenuated mainly by the endothelial nitric oxide - cyclic guanosine monophosphate pathway. In addition, mepivacaine-induced contraction involves cyclooxygenase pathway activation and extracellular calcium influx via voltage-operated calcium channels.     

Sympathetic control of heart rate in nNOS knockout mice

Inhibition of neuronal nitric oxide synthase (nNOS) in cardiac postganglionic sympathetic neurons leads to enhanced cardiac sympathetic responsiveness in normal animals, as well as in animal models of cardiovascular diseases. We used isolated atria from mice with selective genetic disruption of nNOS (nNOS(-/-)) and their wild-type littermates (WT) to investigate whether sympathetic heart rate (HR) responses were dependent on nNOS. Immunohistochemistry was initially used to determine the presence of nNOS in sympathetic [tyrosine hydroxylase (TH) immunoreactive] nerve terminals in the mouse sinoatrial node (SAN). After this, the effects of postganglionic sympathetic nerve stimulation (1-10 Hz) and bath-applied norepinephrine (NE; 10(-8)-10(-4) mol/l) on HR were examined in atria from nNOS(-/-) and WT mice. In the SAN region of WT mice, TH and nNOS immunoreactivity was virtually never colocalized in nerve fibers. nNOS(-/-) atria showed significantly reduced HR responses to sympathetic nerve activation and NE (P < 0.05). Similarly, the positive chronotropic response to the adenylate cyclase activator forskolin (10(-7)-10(-5) mol/l) was attenuated in nNOS(-/-) atria (P < 0.05). Constitutive NOS inhibition with L-nitroarginine (0.1 mmol/l) did not affect the sympathetic HR responses in nNOS(-/-) and WT atria. The paucity of nNOS in the sympathetic innervation of the mouse SAN, in addition to the attenuated HR responses to neuronal and applied NE, indicates that presynaptic sympathetic neuronal NO does not modulate neuronal NE release and SAN pacemaking in this species. It appears that genetic deletion of nNOS results in the inhibition of adrenergic-adenylate cyclase signaling within SAN myocytes.     

肿瘤坏死因子-α诱导心肌肥大中CaN信号通路的作用

目的:研究钙调神经磷酸酶(CaN)信号通路在肿瘤坏死因子-α(TNF-α)诱导心肌细胞肥大中的作用。方法:Lowry法测心肌细胞蛋白含量;计算机图象分析系统测心肌细胞体积;[3H]-亮氨酸掺入法测心肌细胞蛋白合成;Till阳离子测定系统观察胞内[Ca2+]i瞬变;Western blot法测定CaN的表达。结果:①CaN特异性抑制剂CsA(0.2μmol/L)明显抑制TNF-α(100μg/L)诱导的心肌细胞蛋白含量、蛋白合成和细胞体积增大,但对正常心肌细胞生长无影响。②CaN特异性抑制剂CsA(0.2μmol/L)明显降低TNF-α诱导的心肌细胞内钙离子浓度([Ca2+]i)瞬变幅度增高。③TNF-α明显增强心肌细胞内CaN的表达。结论:TNF-α可能通过引起心肌细胞[Ca2+]i升高,促进CaN表达诱导心肌细胞肥大。     

Fructose modulates cardiomyocyte excitation-contraction coupling and Ca²⁺ handling in vitro

Background

High dietary fructose has structural and metabolic cardiac impact, but the potential for fructose to exert direct myocardial action is uncertain. Cardiomyocyte functional responsiveness to fructose, and capacity to transport fructose has not been previously demonstrated.

Objective

The aim of the present study was to seek evidence of fructose-induced modulation of cardiomyocyte excitation-contraction coupling in an acute, in vitro setting.

Methods and Results

The functional effects of fructose on isolated adult rat cardiomyocyte contractility and Ca²⁺ handling were evaluated under physiological conditions (37°C, 2 mM Ca²⁺, HEPES buffer, 4 Hz stimulation) using video edge detection and microfluorimetry (Fura2) methods. Compared with control glucose (11 mM) superfusate, 2-deoxyglucose (2 DG, 11 mM) substitution prolonged both the contraction and relaxation phases of the twitch (by 16 and 36% respectively, p<0.05) and this effect was completely abrogated with fructose supplementation (11 mM). Similarly, fructose prevented the Ca²⁺ transient delay induced by exposure to 2 DG (time to peak Ca²⁺ transient: 2 DG: 29.0±2.1 ms vs. glucose: 23.6±1.1 ms vs. fructose +2 DG: 23.7±1.0 ms; p<0.05). The presence of the fructose transporter, GLUT5 (Slc2a5) was demonstrated in ventricular cardiomyocytes using real time RT-PCR and this was confirmed by conventional RT-PCR.

Conclusion

This is the first demonstration of an acute influence of fructose on cardiomyocyte excitation-contraction coupling. The findings indicate cardiomyocyte capacity to transport and functionally utilize exogenously supplied fructose. This study provides the impetus for future research directed towards characterizing myocardial fructose metabolism and understanding how long term high fructose intake may contribute to modulating cardiac function.