Long-acting calcium channel antagonist pranidipine prevents ventricular remodeling after myocardial infarction in rats

Summary The purpose of this study was to examine the effects of the long-acting calcium channel antagonist pranidipine on ventricular remodeling, systolic and diastolic cardiac function, circulating humoral factors, and cardiac mRNA expression in myocardial infarcted rats. Myocardial infarction (MI) was produced by ligation of the coronary artery in Wistar rats. Three mg/kg per day of pranidipine was randomly administered to the infarcted rats. Hemodynamic measurements, Doppler echocardiographic examinations, analyses of the plasma levels of humoral factors, and myocardial mRNA expression were performed at 4 weeks after myocardial infarction. Left ventricular end-diastolic pressure (LVEDP) and central venous pressure (CVP) increased to 24.2 ± 1.2mmHg and 5.4 ± 0.6mmHg. Pranidipine reduced LVEDP and CVP to 13.6 ± 1.4mmHg (P < 0.01) and 2.5 ± 0.4mmHg (P < 0.01). The weight of the left and right ventricles in MI was significantly higher than in the sham-operated rats (sham, 2.02 ± 0.04 and 0.47 ± 0.02g/kg; MI, 2.18 ± 0.05 and 0.79 ± 0.04g/kg;P < 0.01). Left ventricular end-diastolic dimension (LVDd) in MI increased to 10.3 ± 0.3mm (P < 0.01) (sham, 6.4 ± 0.3mm). Pranidipine prevented an increase in the weight of the left and right ventricles (2.02 ± 0.04 and 0.6 ± 0.03g/kg,P < 0.01) and LVDd (7.9 ± 0.2mm,P < 0.01 to MI). Plasma renin activity (PRA), and plasma epinephrine, norepinephrine, and dopamine concentrations in MI were higher than those of the sham-operated rats. Pranidipine decreased the PRA and plasma cathecolamine levels of the myocardial infarcted rats to the level of the sham-operated rats. Moreover, the rats in MI showed systolic dysfunction, shown by decreased fractional shortening (sham, 31 ± 2% vs MI, 15 ± 1%;P < 0.01) and diastolic dysfunction shown by the E-wave deceleration rate (sham, 12.8 ± 1.1 m/s²; MI, 32.6 ± 2.1m/s²;P < 0.01). Pranidipine significantly prevented systolic and diastolic dysfunction. The increases in β-myosin heavy chain (MHC), α-skeletal actin, and atrial natriuretic polypeptide mRNAs in the noninfarcted left ventricle and right ventricle at 4 weeks after the myocardial infarction were significantly suppressed by the treatment with pranidipine. On the other hand, depressed α-MHC was restored to normal levels by pranidipine in both regions. In conclusion, pranidipine prevents the left ventricular remodeling process accompanied by systolic and diastolic dysfunction, and inhibits abnormal cardiac gene expression after myocardial infarction.     

Pharmacologic inhibition of mast cell degranulation prevents left ventricular remodeling induced by chronic volume overload in rats

BACKGROUND: Left ventricular (LV) hypertrophy and dilation are important compensatory responses to chronic volume overload; however, the mechanisms responsible for this LV remodeling have not been well characterized. Previous observations that the number of myocardial mast cells are increased in congestive heart failure (CHF) suggested the hypothesis that mast cells might be involved in the ventricular remodeling induced by a chronic volume overload. METHODS AND RESULTS: Accordingly, the intent of this study was to determine the contribution of mast cells to LV remodeling, dysfunction, and morbidity/mortality secondary to CHF in the infrarenal aortocaval fistula model of sustained volume overload. To this end, LV end-diastolic pressure, size, and function (ie, isovolumetric pressure-volume relations in the blood-perfused isolated heart) were assessed in both nedocromil sodium treated and untreated rats at 8 weeks after fistula and compared with age-matched controls. Nedocromil, a mast cell-stabilizing drug, effectively prevented the LV dilation and decreased contractility seen in the untreated fistula group in a dose-dependent fashion, resulting in a significant reduction in the incidence of morbidity/mortality from CHF. CONCLUSION: The ability of mast cell stabilization to prevent ventricular dilation induced by chronic volume overload identifies a key role for mast cells in the regulation of myocardial remodeling.     

Differential subcellular actions of ACE inhibitors and AT(1) receptor antagonists on cardiac remodeling induced by chronic inhibition of NO synthesis in rats

Chronic inhibition of NO synthesis induces cardiac hypertrophy independent of systemic blood pressure (SBP) by increasing protein synthesis in vivo. We examined whether ACE inhibitors (ACEIs) enalapril and temocapril and angiotensin II type-I receptor antagonists (angiotensin receptor blockers [ARBs]) losartan and CS-866 can block cardiac hypertrophy and whether changes in activation of 70-kDa S6 kinase (p70S6K) or extracellular signal-regulated protein kinase (ERK) are involved. The following 13 groups were studied: untreated Wistar-Kyoto rats and rats treated with NO synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME), D-NAME (the inactive isomer of L-NAME), L-NAME plus hydralazine, L-NAME plus enalapril (3 mg. kg(-1). d(-1)) or temocapril (1 or 10 mg. kg(-1). d(-1)), L-NAME plus losartan (10 mg. kg(-1). d(-1)) or CS-866 (1 or 10 mg. kg(-1). d(-1)), L-NAME plus temocapril-CS866 in combination (1 or 10 mg. kg(-1). d(-1)), and L-NAME plus rapamycin (0.5 mg. kg(-1). d(-1)). After 8 weeks of each experiment, ratios of coronary wall to lumen (wall/lumen) and left ventricular weight to body weight (LVW/BW) were quantified. L-NAME increased SBP, wall/lumen, and LVW/BW compared with that of control. ACEIs, ARBs, and hydralazine equally canceled the increase in SBP induced by L-NAME. However, ACEIs and ARBs equally (but not hydralazine) attenuated increase in wall/lumen and LVW/BW induced by L-NAME. The L-NAME group showed both p70S6K and ERK activation in myocardium (2.2-fold and 1.8-fold versus control, respectively). ACEIs inactivated p70S6K and ARBs inactivated ERK in myocardium, but hydralazine did not change activation of either kinase. Thus, ACEIs and ARBs modulate different intracellular signaling pathways, inhibiting p70S6K or ERK, respectively, to elicit equal reduction of cardiac hypertrophy induced by chronic inhibition of NO synthesis in vivo.     

Functional remodeling of Ca2+-activated Cl- channel in pacing induced canine failing heart

To determine whether Ca²⁺ activated Cl^-current (I_Cl（Ca）) contributes to the functional remodeling of the failing heart. Methods Whole cell patch-clamp recording technique was employed to record the I_Cl（Ca） in cardiac myocytes enzymatically isolated from rapidly pacing induced canine failing hearts at room temperature and compared that of the normal hearts （Nor）.Results The current density of DIDS （200M） sensitive I_Cl（Ca） induced by intracellular Ca²⁺ release trigged by L-type Ca²⁺ current (I_Ca,L) was significantly decreased in heart failare （HF） cells compared to Nor cells.At membrane voltage of 20mV,the I_Cl（Ca） density was 3.02±0. 54 pA/pF in Nor （n=6） vs.1.31±0.25 pA/pF in HF （n=8） cells,（P<0.01）,while the averaged I_Ca,L density did not show difference between two groups.The time constant of current decay of I_Cl（Ca） was similar in both types of cells.On the other hand,in intra cellular Ca²⁺ clamped mode,where the [Ca²⁺]_i was maintained at 100nmol/L,I_Cl（Ca） density be increased significantly in HF cells when the membrane voltage at +30mV or higher.Conclusions Our results suggest that I_Cl（Ca） density was decreased in pacing induced failing heart but the channel function be enhanced.Impaired Ca²⁺ handing in HF cells rather than reduced I_Cl（Ca） channel function itself may have caused this abnormality.The I_Cl（Ca） density reduction might contribute to the prolongation of action potential in failing heart.The I_Cl（Ca） channel function up-regulation is likely to cause cardiac arrhythmia by inducing a delayed after depolarization,when Ca²⁺ overload occurred in diastolic failing heart cells.     

Effects of Ca^2＋ channel blockers on store-operated Ca^2＋ channel currents of Kupffer cells after hepatic ischemia/reperfusion injury in rats

AIM: To study the effects of hepatic ischemia/reperfusion (I/R) injury on store-operated calcium channel (SOC) currents (I(SOC)) in freshly isolated rat Kupffer cells, and the effects of Ca(2+) channel blockers, 2-aminoethoxydiphenyl borate (2-APB), SK and F96365, econazole and miconazole, on I(SOC) in isolated rat Kupffer cells after hepatic I/R injury. METHODS: The model of rat hepatic I/R injury was established. Whole-cell patch-clamp techniques were performed to investigate the effects of 2-APB, SK and F96365, econazole and miconazole on I(SOC) in isolated rat Kupffer cells after hepatic I /R injury. RESULTS: I/R injury significantly increased I(SOC) from -80.4 +/- 25.2pA to -159.5 +/- 34.5pA ((b)P < 0.01, n = 30). 2-APB (20, 40, 60, 80, 100 micromol/L), SK and F96365 (5, 10, 20, 40, 50 micromol/L), econazole (0.1, 0.3, 1, 3, 10 micromol/L) and miconazole (0.1, 0.3, 1, 3, 10 micromol/L) inhibited I(SOC) in a concentration-dependent manner with IC50 of 37.41 micromol/L (n = 8), 5.89 micromol/L (n = 11), 0.21 micromol/L (n = 13), and 0.28 micromol/L (n = 10). The peak value of I(SOC) in the I-V relationship was decreased by the blockers in different concentrations, but the reverse potential of I(SOC) was not transformed. CONCLUSION: SOC is the main channel for the influx of Ca(2+) during hepatic I/R injuries. Calcium channel blockers, 2-APB, SK and F96365, econazole and miconazole, have obviously protective effects on I/R injury, probably by inhibiting I(SOC) in Kupffer cells and preventing the activation of Kupffer cells.     

醛固酮诱导的心肌重构及非洛地平的干预作用

目的 研究非洛地平（felodipine,Fel）在醛固酮（aldosterone,Ald）诱导的心肌重构中的保护作用及其可能的机制。方法 SD大鼠32只随机分为4组（每组n=8）,即对照组、Ald组、Ald+Fel组和Ald+螺内酯（spironolactone,Spi）组。Ald组:以Ald 18 μg/d皮下注射,连续4周;对照组:注射等量生理盐水4周;Ald+Fel组:以Ald 18 μg/d皮下注射,同时给于Fel 5 mg/(kg·d)灌胃,连续4周;Ald+Spi组:以Ald 18 μg/d皮下注射, 同时给予Spi 20 mg/(kg·d)灌胃,连续4周。比较各组大鼠的左心室质量(LVW)及全心质量(HW)与体质量(BW)的比值,心肌组织匀浆超氧化物歧化酶（SOD）和丙二醛（MDA）的含量,心肌胶原面积（CA）,以及心肌细胞凋亡指数（AI）。结果 与Ald组相比, 对照组、Ald+Fel组和Ald+Spi组大鼠的LVW/BW,HW/BW,CA和AI均减少,对照组和Ald+Spi组大鼠MDA的含量较Ald组减少,SOD的含量较Ald组增加（P<0.01）;Ald+Fel组大鼠SOD和MDA的含量与Ald组相比无明显差异。结论 Fel能够改善Ald诱导的心肌肥大和心肌细胞凋亡,但不能改善Ald诱导的氧化应激水平的增加。     

Ca2+ mobilization induced by ouabain in thymocytes involves intracellular and extracellular Ca2+ pools

Immune dysfunction has been reported in hypertensive rats, and circulating levels of ouabain are increased in some experimental models of hypertension. Ouabain is an inhibitor of the Na+/K+-ATPase capable of diverse effects on cells of the immune system, but its mode of action on these cells is still unknown. The levels of cytoplasmic calcium ions play an important role in cell signaling, and ouabain may induce an increase in intracellular calcium indirectly through the Na+/Ca2+ exchanger. The current work examined the possibility that this drug could be exerting its effects on thymocytes through calcium mobilization and an increase in the cytosolic calcium concentration. Intracellular calcium was evaluated by using Balb-c mouse thymocytes loaded with FURA-2. Both intracellular and extracellular calcium pools were mobilized by ouabain (3 to 1000 nmol). The influx of extracellular calcium depended on the Na+/Ca2+ exchanger and on voltage-dependent calcium channels, as it was inhibited by amiloride and benzamil, consistent with the inhibition of the Na+/K+ pump. In addition, the increase of calcium from intracellular stores was extremely rapid. Furthermore, an increase in cytosolic calcium levels was obtained with the combination of ouabain and thapsigargin, which was greater than that seen with either drug alone. Our data suggest that low concentrations of ouabain may be acting on thymocytes through a mechanism different from the traditional inhibition of the Na+/K+-ATPase, as the cytosolic calcium rise was partly dependent on the release from intracellular stores.     

Tea catechins attenuate chronic ventricular remodeling after myocardial ischemia in rats

Tea catechins have many biological functions; these effects are induced by the suppression of several inflammatory factors. However, the effects of catechins on ventricular remodeling after myocardial ischemia have not been well investigated. To test the hypothesis that catechins can attenuate chronic ventricular remodeling after myocardial ischemia, we performed oral administration of catechins into rat myocardial ischemia models. We analyzed the mechanisms using physiological, pathological and molecular examinations. Although severe myocardial fibrosis with enhancement of inflammatory factors were observed in the non-treated ischemia group on day 28, catechins attenuated these changes with suppressed NF-kappaB and matrix metalloproteinases without systemic adverse effects. Catechins are potent for the suppression of chronic ventricular remodeling after myocardial ischemia because they are critically involved in the suppression of several inflammatory genes.     

Up-regulation of myocardial L-type Ca2+ channel in chronic alcoholic subjects without cardiomyopathy

BACKGROUND: Excessive ethanol intake is one of the most frequent causes of acquired dilated cardiomyopathy in developed countries. L-type Ca(2+) channels, involved in excitation-contraction coupling, are disturbed in animal models of persistent ethanol consumption. This study was designed to evaluate the density and function of myocardial L-type Ca(2+) channel receptors in organ donors with chronic alcoholism and controls. METHODS: The protein expression of L-type Ca(2+) channels was determined with (3)H-(+)-PN 200-110-binding experiments using a specific antibody against the alpha(1)-subunit in homogenate samples of left-ventricle apex from organ donors: healthy controls (n=11), chronic alcoholic without cardiomyopathy (n=12), and alcoholics with cardiomyopathy (n=11). Morphometric measurements of cardiomyocytes were performed. RESULTS: Binding experiments proved an up-regulation of L-type Ca(2+) channels expression in alcoholic patients compared with controls (B(max) 2.61 +/- 1.10 vs 1.33 +/- 0.49 fmol/mg, respectively; p<0.001). This up-regulation was present in the group of alcoholic subjects without cardiomyopathy, and was not seen in those with cardiomyopathy (3.39 +/- 2.20 vs 1.77 +/- 0.53 fmol/mg, respectively; p=0.02). The cross-sectional area and perimeter of the cells were greater in alcoholic patients with cardiomyopathy compared with controls and alcoholic patients without cardiomyopathy (500 +/- 87 vs 307 +/- 74 and 255 +/- 25 microm(2), respectively; p<0.001 both) as was the perimeter (78.7 +/- 7.7 vs 61.5 +/- 7.2 and 56.5 +/- 2.8 microm, respectively; p<0.001 both). Binding results did not change after adjusting receptor measurements for cross-sectional area and cell perimeter. CONCLUSIONS: Chronic alcoholism causes an up-regulation of myocardial L-type Ca(2+) channel receptors, which decreases when cardiomyopathy is present.     

Angiotensin II type 1 receptor blocker prevents atrial structural remodeling in rats with hypertension induced by chronic nitric oxide inhibition.

The prevalence of atrial fibrillation (AF) increases in patients with hypertension. Angiotensin II is involved in structural atrial remodeling, which contributes to the onset and maintenance of AF in paced animal models. We investigated the role of angiotensin II in atrial structural remodeling in rats with hypertension. Ten-week-old male Wistar-Kyoto rats were randomly divided into 4 groups: a control group (no treatment), an Nomega-nitro-L-arginine methyl ester (L-NAME) group (administered L-NAME, an inhibitor of nitric oxide synthase, 1 g/l in drinking water), an L-NAME+candesartan group (L-NAME plus candesartan-an angiotensin II receptor blocker (ARB)-at 0.1 mg/kg/day), and an L-NAME + hydralazine group (L-NAME plus hydralazine at 120 mg/l in drinking water). Eight weeks after treatment, the L-NAME group showed significantly higher systolic blood pressure than the control group (197 +/- 12 vs.138 +/- 5 mmHg, p < 0.05). Candesartan or hydralazine with L-NAME reduced systolic blood pressure to baseline. Chronic inhibition of NO synthesis increased the extent of fibrosis and transforming growth factor-beta expression in atrial tissue, and both of these effects were prevented by candesartan, but not by hydralazine. Cardiac hypertrophy and dysfunction were induced in the L-NAME group, and these effects were also prevented by candesartan, but not by hydralazine. In contrast, the decrease in thrombomodulin expression in the atrial endocardium in hypertensive rats was restored by candesartan and hydralazine. The ARB prevented atrial structural remodeling, a possible contributing factor for the development of AF, in the hearts of rats with hypertension induced by long-term inhibition of NO synthesis.     

Endurance training in rats with chronic heart failure induced by myocardial infarction

The response to exercise was investigated in trained and sedentary rats with moderate compensated heart failure produced by myocardial infarction (MI) and in rats that underwent sham operations. Trained rats ran on a treadmill (10% grade at 20 m/min) for 60 min/day, 5 days/week for 10 to 12 weeks, whereas sedentary rats had only limited activity. Maximal oxygen consumption normalized for body weight (ml kg-1 min-1) was determined for each rat and found to be (1) greater in trained rats when compared with sedentary rats and (2) greater in sham-operated rats when compared with their counterparts that suffered infarction. In addition, skeletal muscle succinate dehydrogenase activities were greater and the blood lactic acid response to submaximal exercise was lower in trained rats compared with sedentary rats. Left ventricular infarct size for sedentary and trained rats with infarction was 36 +/- 3% and 34 +/- 3% of the total endocardial circumference, respectively, and resulted in (1) elevated left ventricular end-diastolic pressures at rest and during exercise, (2) lower mean arterial pressures at rest, and (3) lower maximal heart rates when compared with those in their sham-operated counterparts. However, normalization of mean arterial pressures during submaximal and maximal exercise was found along with a trend toward normalization of maximal heart rate when trained rats with infarction were compared with their sedentary counterparts. Blood flows to the kidneys, organs of the gut, and skeletal muscle during both submaximal and maximal exercise were unaffected by either myocardial infarction or training; no differences between sedentary and trained rats with infarction and sedentary and trained sham-operated rats were found. These results demonstrate that an exercise training program of moderate intensity produces beneficial hemodynamic and metabolic effects in rats with moderate compensated heart failure.     

脂联素对大鼠慢性间歇性低氧所致心肌重塑的影响

目的：探讨慢性间歇性低氧（chronic intermittent hypoxia,CIH）对心肌重塑的影响及脂联素（adiponectin, Ad）的干预作用。方法将45只Wistar大鼠随机分为3组：正常对照组（NC）,CIH组和CIH＋Ad组。CIH 35d后,使用马松染色分析方法检测左室纤维化程度及使用Western blot方法来衡量Ⅰ型胶原蛋白、Ⅲ型胶原蛋白和TGF-β/smad2/3通路蛋白的表达。通过RT-PCR方法来研究基质金属蛋白酶-2（MMP2）/基质金属蛋白酶的组织抑制剂-2（TIMP-2）的mRNA表达比值情况。结果慢性间歇性低氧处理后,CIH组左心室的纤维化程度显著高于NC组和CIH＋Ad组（P＜0.05）,但NC组和CIH＋Ad组之间差异具有统计学意义（P＜0.05）。CIH组Ⅰ型胶原蛋白和Ⅲ型胶原蛋白和MMP2/TIMP-2的mRNA比值表达最高,NC组表达最低,CIH＋Ad组居中,3组之间均差异具有统计学意义（P＜0.05）。TGF-β/smad通路蛋白在CIH组中表达显著高于NC组和CIH组（P＜0.05）,且NC组和CIH＋Ad组差异具有统计学意义（P＜0.05）。结论慢性间歇性低氧可引起左室重构,而Ad可能通过抑制TGF-β/smad2/3通路改善此损害。     

Cellular basis of chronic ventricular remodeling after myocardial infarction in rats.

To determine whether the hypertrophic response of the surviving myocardium after infarction leads to normalization of ventricular hemodynamics and wall stress, the left coronary artery was ligated in rats. One month later, the rats were killed. In infarcts affecting an average 38% of the free wall of the left ventricle (small infarcts), reactive hypertrophy in the spared myocardium bordering and remote from the scar was documented by increases in myocyte cell volume per nucleus of 43% and 25%, respectively. These cellular enlargements resulted in a complete reconstitution of functioning tissue. However, left ventricular end-diastolic pressure was increased, left ventricular dP/dt was decreased, and diastolic wall stress was increased 2.4-fold. After infarctions resulting in a 60% loss of mass (large infarcts), myocyte hypertrophy was 81% and 32% in the regions adjacent to and distant from the scar, respectively. A 10% deficit was present in the recovery of viable myocardium. Functionally, ventricular performance was markedly depressed, and diastolic wall stress was increased ninefold. The alterations in loading of the spared myocardium were due to an increase in chamber volume and a decrease in the myocardial mass/chamber volume ratio that affected both infarct groups. Chamber dilation was the consequence of the combination of gross anatomic and cellular changes consisting, in the presence of small infarcts, of a 6% and a 19% increase in transverse midchamber diameter and in average myocyte length per nucleus, respectively. In the presence of large infarcts, transverse and longitudinal chamber diameters expanded by 27% and 11%, respectively, myocyte length per nucleus expanded by 26%, and the mural number of myocytes decreased by 10%. In conclusion, decompensated eccentric ventricular hypertrophy develops chronically after infarction, and growth processes in myocytes are inadequate for normalization of wall stress when myocyte loss involves nearly 40% or more of the cells of the left ventricular free wall. The persistance of elevated myocardial and cellular loads may sustain the progression of the disease state toward end-stage congestive heart failure.     

Chronic SR Ca2+-ATPase inhibition causes adaptive changes in cellular Ca2+ transport

Phospholamban, the critical regulator of the cardiac SERCA2a Ca2+ affinity, is phosphorylated at Ser16 and Thr17 during beta-adrenergic stimulation (eg, isoproterenol). To assess the impact of nonphosphorylatable phospholamban, a S16A, T17A double-mutant (DM) was introduced into phospholamban knockout mouse hearts. Transgenic lines expressing DM phospholamban at levels similar to wild types (WT) were identified. In vitro phosphorylation confirmed that DM phospholamban could not be phosphorylated, but produced the same shift in EC50 of SERCA2a for Ca2+ as unphosphorylated WT phospholamban. Rates of basal twitch [Ca2+]i decline were not different in DM versus WT cardiomyocytes. Isoproterenol increased the rates of twitch [Ca2+]i decline in WT, but not DM myocytes, confirming the prominent role of phospholamban phosphorylation in this response. Increased L-type Ca2+ current (ICa) density, with unaltered characteristics, was the major compensation in DM myocytes. Consequently, the normal beta-adrenergic-induced increase in ICa caused larger dynamic changes in absolute ICa density. Isoproterenol increased Ca2+ transients to a comparable amplitude in DM and WT. There were no changes in myofilament Ca2+ sensitivity, or the expression levels and Ca2+ removal activities of other Ca2+-handling proteins. Nor was there evidence of cardiac remodeling up to 10 months of age. Thus, chronic inhibition of SERCA2a by ablation of phospholamban phosphorylation (abolishing its adrenergic regulation) results in a unique cellular adaptation involving greater dynamic ICa modulation. This ICa modulation may partly compensate for the loss in SERCA2a responsiveness and thereby partially normalize beta-adrenergic inotropy in DM phospholamban mice.     

姜黄素防止慢性酒精中毒导致的肝损伤

目的观察酒精性肝病大鼠肝中核因子κB(nuclear factorκB,NFκB),单核细胞趋化蛋白-1(monocyte chemoattractan tpro-tein-1,MCP-1),巨噬细胞炎症蛋白-2(macrophage inflammation protein-2,MIP-2)的表达,探讨姜黄素(curcumin)是否能降低酒精性肝病大鼠肝组织中NFκB依赖的基因表达,抑制脂质过氧化(lipid peroxidation)从而防止或减轻酒精性肝损伤(alcoholic liver disease,ALD).方法随机将32只Sprague Dawley大鼠分成四组(8只/组),乙醇喂养组(E组),乙醇加姜黄素喂养组(EC组),姜黄素加蔗糖喂养组(DC组),蔗糖喂养组(D组),分别在饮水中加入乙醇(50%,vol/vol)和等热量的蔗糖,姜黄素(75 mg·kg-1·d-1)加工进食物中.四组大鼠于12周时测定其血清中ALT,AST浓度及其肝组织中MDA含量,同时用RT-PCR测定肝组织中MCP-1,MIP-2mRNA的表达,用免疫组化方法测定肝组织中NFκB,MCP-1的表达,并在光学显微镜下观察肝脏的形态学改变.结果乙醇喂养组中大鼠血清ALT,AST分别为73.7±14.3U/L和154 34±24.6U/L明显高于乙醇加姜黄素组的32.1±11.8U/L和60.3±10.8U/L(P＜0.01);乙醇喂养组大鼠肝组织中MDA水平为1.04±0.08nmol/mg也高于乙醇加姜黄素组中的0.51±0.03nmol/mg(P＜0.01).免疫组化结果显示乙醇组大鼠肝组织中有NFκB,MCP-1表达,而其它三组大鼠肝组织中无或有弱表达;乙醇组大鼠肝组织有MCP-1,MIP2mRNA表达,其肝组织发生显著的病理变化,主要表现为脂肪变性,炎性细胞浸润及少数肝细胞坏死,其余三组大鼠肝组织无表达,病理改变不明显.结论姜黄素能抑制慢性酒精中毒大鼠肝组织中NFκB依赖的基因表达,抑制脂质过氧化,从而防止酒精诱导的肝损伤.     

Ca2+ channel blockers stimulate ileal and colonic water absorption

The effects of calcium channel blockers on water transport in the rat ileum and distal colon were studied in vivo using the single-pass perfusion technique. Parenteral but not intraluminal verapamil, and parenteral nifedipine increased ileal water absorption, with effects lasting at least 60 min. In contrast, i.p. verapamil had no effect on rat distal colonic water absorption, whereas intraluminal verapamil significantly stimulated colonic water absorption. Similarly, perfusing the rat descending colon with low-Ca2+ Ringer's-HCO3 stimulated colonic water absorption. Verapamil was not antisecretory because the theophylline-induced decrease in ileal water transport was similar in control animals and in animals pretreated with i.p. verapamil. In addition, nifedipine stimulated active Na and Cl absorption in rabbit ileum. These studies demonstrate that the Ca2+ channel blockers verapamil and nifedipine stimulate basal absorption of water in rat ileum and distal colon in vivo, and stimulate active Na and Cl absorption in rabbit ileum in vitro. The verapamil stimulation of colonic water absorption from the luminal surface was duplicated by perfusion with a low-Ca2+ bathing solution. This suggests the presence of apical membrane Ca2+ channels in rat colon, which appear to be involved in regulation of basal water transport, and that these Ca2+ channels are in a partially open state under basal conditions. Because verapamil stimulates absorption systemically (ileum) as well as intraluminally (colon), Ca2+ channel blockers have properties that might be useful in treatment of diarrheal diseases.     

Ca2+-induced inhibition of the cardiac Ca2+ channel depends on calmodulin

Ca2+-induced inhibition of alpha1C voltage-gated Ca2+ channels is a physiologically important regulatory mechanism that shortens the mean open time of these otherwise long-lasting high-voltage-activated channels. The mechanism of action of Ca2+ has been a matter of some controversy, as previous studies have proposed the involvement of a putative Ca2+-binding EF hand in the C terminus of alpha1C and/or a sequence downstream from this EF-hand motif containing a putative calmodulin (CaM)-binding IQ motif. Previously, using site directed mutagenesis, we have shown that disruption of the EF-hand motif does not remove Ca2+ inhibition. We now show that the IQ motif binds CaM and that disruption of this binding activity prevents Ca2+ inhibition. We propose that Ca2+ entering through the voltage-gated pore binds to CaM and that the Ca/CaM complex is the mediator of Ca2+ inhibition.     

钙及钙库操控性通道与肺血管重塑

肺血管重塑是指由于血管平滑肌细胞增殖能力增强、凋亡能力减弱、细胞外基质异常堆积所致的血管壁增厚、管腔狭窄并阻塞的现象。血管平滑肌细胞根据其结构和功能不同，分为收缩型和合成型两种表型，两型之间存在过渡型细胞。肺血管平滑肌细胞具有表型双向调控能力。收缩型血管平滑肌细胞不能增殖，合成型血管平滑肌细胞缺乏收缩能力，但却具有很强的增殖能力，只有向合成型转化的血管平滑肌细胞才能对有丝分裂原起反应而增殖。     

Alterations in the inotropic responses to forskolin and Ca2+ and reduced gene expressions of Ca2+-signaling proteins induced by chronic volume overload in rabbits

Volume overload results in eccentric cardiac hypertrophy, but it is still unknown how this mechanical overload modulates the inotropic response to exogenous Ca2+ or adenylyl cyclase stimulation. Inotropic responsiveness in vivo and the levels of gene expression of Ca2+ signaling proteins were studied in rabbit hearts hypertrophied as a result of volume overload at 4 and 12 weeks after arteriovenous shunt formation. In sham-operated control rabbits, left ventricular (LV)+dP/dt was augmented in response to graded doses of CaCl2. Dose-related changes of LV+dP/dt to CaCl2 were attenuated significantly in shunt rabbits with volume overload. Forskolin dose-dependently augmented LV+dP/dt in sham rabbits, which was also attenuated significantly in rabbits with volume overload. The mRNA levels of dihydropyridine receptor, Na+/Ca2+ exchanger, sarcoplasmic reticulum Ca2+-ATPase, and ryanodine receptor decreased significantly at 4 and 12 weeks in the volume-overload rabbits compared with the sham rabbits, but the mRNA levels of phospholamban and calsequestrin remained unchanged. Chronic volume overload alters contractile responsiveness to Ca2+ or adenylyl cyclase stimulation, and downregulation of steady state mRNA levels of Ca2+ signaling proteins might be, at least in part, related to this pathologic process.