Ginkgo biloba leaf extract reverses amyloid beta-peptide-induced isoprostane production in rat brain in vitro

Isoprostanes are prostaglandin (PG) isomers generated from oxygen radical peroxidation of arachidonic acid, which are reliable markers of membrane oxidative damage. Aging is characterized by an imbalance between the generation of reactive oxygen species and antioxidant detoxification pathways. Ginkgo biloba leaf extract is reputed as a neuroprotective antioxidant agent. We have tested the effects of a Ginkgo biloba extract {containing 24.1 % flavonoids and 181 % terpene lactones [bilobalide (0.542 %), ginkgolide A (0.570 %), ginkgolide B (0.293 %), ginkgolide C (0.263 %), and ginkgolide J (0.138 %)]} on the production of 8-iso-PGF2alpha from rat brain synaptosomes obtained from young (3 months old) or aged (12 and 24 months old) rats, both in the basal state and after oxidative stress induced by either hydrogen peroxide or amyloid beta-peptide. Our findings show that Ginkgo biloba extract pretreatment is able to completely reverse both basal and hydrogen peroxide-stimulated isoprostane production (IC50 of 81.92 microM and 31.89 microM, respectively). Amyloid beta-peptide-induced isoprostane production was also inhibited, both in young and aged rats, to a level even lower than that in unstimulated synaptosomes. This suggests that the oxygen radical scavenging properties of the Ginkgo biloba extract are fully effective in young, as well as in old rats, showing a greater inhibition of isoprostane production in the latter.     

Existence of a distinct concentration window governing daunorubicin-induced mammalian liver mitotoxicity--implication for determining therapeutic window

Daunorubicin (DNR) is a well known anticancer drug believed to act mainly by topoisomerase II inhibition and mitochondria-mediated free radical generation. Though several studies were dedicated to elucidate the mechanism of action of DNR, however the mechanism still remains illusive. DNR is reported to affect mitochondrial respiration. However, there are contradictory reports regarding DNR effect on oxygen consumption. Interestingly, DNR at low concentration (<10 microM) dose-dependently augments respiration but at higher concentration inhibits respiration. To investigate, if a concentration window exists in which the effect of DNR on mitochondria is optimum, dose-dependent effect of DNR on mitochondria was studied. DNR inhibited electron transfer and generates reactive oxygen species (ROS) at complex I and III but not at complex II. DNR-induced ROS generation was found instrumental in mitochondrial membrane potential collapse and mitochondrial permeability transition (MPT) opening. MPT closure reduced the observed respiratory burst. Thus, at lower DNR concentration, MPT opening leads to a sudden burst of respiration while at higher concentration electron transfer gets inhibited, therefore respiration gets repressed. We for the first time, provide a possible explanation for the reports regarding the differential regulation of respiration by DNR. Thus, further establishing the concept of concentration window and justifying the need for dose optimization for maximal therapeutic effect.     

BILOBALIDE AND NEUROPROTECTION

In vivo studies have indicated that systemically administered bilobalide, a sesquiterpene trilactone constituent of Ginkgo biloba leaf extracts, can reduce cerebral edema produced by triethyltin, decrease cortical infarct volume in certain stroke models, and reduce cerebral ischemia. In vitro and ex vivo studies indicate that bilobalide has multiple mechanisms of action that may be associated with neuroprotection, including its preservation of mitochondrial ATP synthesis, its inhibition of apoptotic damage induced by staurosporine or by serum-free medium, its suppression of hypoxia-induced membrane deterioration in the brain, and its actions of increasing the expression of the mitochondrial DNA-encoded COX III subunit of cytochrome c oxidase and the ND1 subunit of NADH dehydrogenase. As multiple modes of action may apply to bilobalide, it could be useful in developing therapy for disorders involving cerebral ischemia and neurodegeneration.     

Tributyltin (TBT) and mitochondrial respiration in mussel digestive gland

The toxicity of organotins and especially tri-n-butyltin (TBT) on mitochondria is well known. However as far as we are aware, effects on mitochondrial respiration are unexplored in mollusks. In this work mitochondria isolated from the digestive gland of Mytilus galloprovincialis and susceptive to the classical respiratory chain inhibitors, were assayed in the presence of micromolar TBT concentrations to investigate mitochondrial respiratory activities. Intact and freeze-thawed mitochondria were used. TBT significantly inhibited oxygen consumption in the presence of glutamate/malate or succinate as substrates. Conversely cytochrome c oxidase activity (complex IV), assayed both polarographically and spectrophotometrically, was unaffected. The addition of 1,4-dithioerythritol (DTE) decreased the TBT-driven inhibition of complexes I and III. The TBT capability of covalent binding to thiol groups of mitochondrial proteins in a dose-dependent manner was confirmed by the aid of Ellman’s reagent. Data strongly suggests that TBT may prevent the electron transfer from complexes I and III to downhill respiratory chain complexes by binding to critical SH residues.     

Protective effect of trimetazidine on myocardial mitochondrial function in an ex-vivo model of global myocardial ischemia

Trimetazidine is an anti-ischemic drug whose cytoprotective mechanisms are not yet fully understood (but until now mainly related to the trimetazidine-induced "metabolic shift" from lipid beta-oxidation to glucose aerobic oxidation). We studied the effect of trimetazidine on the mitochondrial function of ischemic Wistar rat hearts perfused with glucose, using a model of ex-vivo perfusion (Langendorff system). We measured the electrical potential of the mitochondrial membrane, O2 consumption by the respiratory chain, energy charges generated and the enzyme activities of the respiratory chain complexes. In this model, trimetazidine had a preferential action on the oxidative system (mainly on complex I), increasing its enzyme activity and decreasing O2 consumption after phosphorylation; this could decrease oxygen free radical production and increase mitochondrial integrity, thus allowing the maintenance of the electrical potential. These results allow us to better understand the cytoprotective effects of trimetazidine in coronary artery disease.     

银杏叶提取物对糖尿病大鼠心肌线粒体呼吸控制率的影响

目的观察银杏叶提取物(EGb)对糖尿病大鼠心肌线粒体呼吸控制率的影响。方法30只SD大鼠随机分为正常对照组、糖尿病组和银杏叶治疗组,观察各组大鼠心肌线粒体超微结构,心肌线粒体呼吸控制率的变化。结果糖尿病大鼠心肌线粒体主要表现为肿胀,嵴变短,空泡化;呼吸控制率3态呼吸降低,呼吸控制率降低。银杏叶治疗组病变较糖尿病组明显减轻,治疗组心肌线粒体呼吸控制率3态呼吸及呼吸控制率与正常对照组无明显差异。结论EGb能提高心肌线粒体的呼吸控制率,从而对糖尿病大鼠心肌起保护作用。     

Analysis of ginkgolides and bilobalide in Ginkgo biloba L. extract injections by high-performance liquid chromatography with evaporative light scattering detection

A RP-HPLC method with evaporative light scattering detection (ELSD) was developed for the determination of ginkgolides and bilobalide in Ginkgo biloba L. extract injections. The samples were extracted with ethyl acetate and the resulting extract was purified by aluminum oxide column. The resultant solution was determined by HPLC on a C(18) column with methanol-water (33:67, v/v) as eluent. The optimum ELSD parameters were set. The recovery of the method was between 98.3 and 102.1%. The method is suitable for routine quantitation of terpenes in Ginkgo biloba L. extract injections.     

Mitochondrial complex I as a novel target for intraneuronal DA: Modulation of respiration in intact cells

Accumulating evidence suggests a role for mitochondria in synaptic potentiation and neurotransmission as well as in morphogenesis and plasticity of spines and synapses. However, studies investigating the ability of neurotransmitters to reciprocally affect mitochondrial function are sparse. In the present study we investigated whether dopamine can affect mitochondrial function in intact neuronal cells. We have shown that short- or long-term exposure of human neuroblastoma SH-SY5Y cells to dopamine (DA) inhibited mitochondrial respiration. This inhibition was associated with an increase in DA intracellular levels, and was prevented by the DA membrane transporter inhibitors, cocaine and GBR-12909. DA inhibited respiration driven through complex I but not through complexes II or III, in line with DA ability to specifically inhibit complex I activity in mitochondrial preparations. The effect of DA on complex I was not associated with altered expression of three subunits of complex I, which were formerly reported abnormal in DA-related pathologies. DA effects on respiration were not due to its ability to form reactive oxygen species. Antipsychotic drugs, which compete with DA on its receptors and inhibit complex I activity, also decreased complex I driven mitochondrial respiration. These findings may suggest that DA, which is taken up by neurons, can affect mitochondria and thereby neurotransmission and synaptic plasticity. Such a mechanism may be of relevance to DA-related non-degenerative pathologies such as schizophrenia.     

Effects of resveratrol on the rat brain respiratory chain.

The aim of this work was to investigate the possible effects of resveratrol on the mitochondrial respiratory chain in rat brains. Isolation of mitochondria was performed at 4 degrees C using differential centrifugation. Mitochondrial respiration rate (0.4 mg of protein/ml) was determined by measuring mitochondrial oxygen consumption with a Clark electrode at 37 degrees C. Respiratory control ratio (RCR) was evaluated as the state 3/state 4 ratio of oxidative phosphorylation with substrates adenosine 5'-diphosphate (ADP) and malate plus glutamate, respectively in the presence and in the absence of resveratrol. The rate of oxygen consumption by the different complexes was checked using rotenone (2 microM), malonate (10 mM), antimycin A (1 microM), potassium cyanide (KCN) (0.3 mM) and oligomycin (10 microM) to inhibit complexes II, III, IV, V and I, respectively. Moreover, enzyme activity determinations were checked as follows: the activities of complexes II-III were measured as the rate of cytochrome c reduction at 550 nm (37 degrees C) successively triggered either by succinate (complexes II and III) or by decylubiquinol (DUQH2) (complex III), in the presence and in the absence of resveratrol. Adenosine 5'-triphosphate (ATP) synthase activity was checked as ATP hydrolysis (ATPase) at 37 degrees C for 10 min from purified mitochondria on Percoll gradient. The inorganic phosphate (Pi) concentration was measured by the Fiske and Subbarow method. When complexes I to V were activated by glutamate plus malate, resveratrol (10(-11) - 10(-4) M) significantly decreased RC (p < 0.001) following a biphasic curve with two EC50 values, 0.162 +/- 0.072 microM and 24.5 +/- 4.0 microM, representing about 56% of total oxygen consumption inhibition. We also observed a concentration-dependent effect on state 3 with two EC50 values, 2.28 +/- 0.87 nM and 27 +/- 5 microM respectively. On the other hand, resveratrol inhibited state 4 following a concentration-dependent curve with an EC50 of 37 +/- 11 microM. When complex IV operated alone, resveratrol (100 microM) did not modify oxygen consumption compared with control, indicating that this molecule did not inhibit complex IV. Thus resveratrol inhibits the mitochondrial respiratory chain through complexes I to III. In order to confirm these data, we measured the enzymatic activity of ubiquinol cytochrome c reductase alone and in the presence of resveratrol. In the presence of disrupted mitochondria, after freeze thawing cycles (three times), resveratrol inhibited about 20% of complex III activity. These results suggest that resveratrol and DUQH2 could be competitive on complex III. Resveratrol significantly inhibited ATPase activity (p < 0.001) following a biphasic curve with two EC50 values, 0.39 +/- 0.15 nM and 23.1 +/- 6.4 microM, both representing about 80% of oligomycin-dependent ATPase total activity. Resveratrol was effective as a protecting agent on the three models of oxidation. On lipid peroxidation of brain synaptosomes induced by the Fenton reaction, it was three times more potent than DUQH2. Its effectiveness in reducing 1,1-diphenyl-2-picryl hydrazyl radical (DPPH degrees) showed a stoichiometry of two, indicating that two hydrogen atoms of resveratrol were abstracted by the process. Resveratrol was also able to scavenge the superoxide anion (O2 degrees) generated from rat forebrain mitochondria in a concentration dependent manner. In conclusion, resveratrol can decrease complex III activity by competition with coenzyme Q. This property is especially interesting as this complex is the site where reactive oxygen substances (ROS) are generated. By decreasing the activity of complex III, resveratrol cannot only oppose the production of ROS but can also scavenge them.     

Effect of Stryphnodendron adstringens (barbatimão) on energy metabolism in the rat liver

The action of a barbatim?o extract on hepatic energy metabolism was investigated using isolated mitochondria and the perfused rat liver. In mitochondria the barbatim?o extract inhibited respiration in the presence of ADP and succinate. Stimulation occurred, however, after ADP phosphorylation (state IV respiration). The ADP/O and respiratory control ratios were reduced. The activities of succinate-oxidase, NADH-oxidase and the oxidation of ascorbate were inhibited. The ATPase of intact mitochondria was stimulated, but the ATPases of uncoupled and disrupted mitochondria were inhibited. In perfused livers the extract caused stimulation of oxygen consumption, inhibition of gluconeogenesis and stimulation of glycolysis. Glucose release due to glycogenolysis was stimulated shortly after the introduction of the extract, but inhibition gradually developed as the infusion was continued. Apparently the barbatim?o extract impairs the hepatic energy metabolism by three mechanisms: (1) uncoupling of oxidative phosphorylation, (2) inhibition of mitochondrial electron transport, and (3) inhibition of ATP-synthase.     

Effect of triclosan (TRN) on energy-linked functions of rat liver mitochondria

Bisphenols are a class of compounds that exhibit a broad spectrum of antimicrobial activity. One of the most widely used member of this group is triclosan (TRN). TRN is a synthetic, non-ionic, broad-spectrum antimicrobial agent, which is incorporated into several products, including hand soaps and detergents and those of skin care and oral hygiene. The effects of TRN on mitochondrial respiratory parameters and the inner mitochondrial membrane potential (DeltaPsi) are described. That of TRN (up to 60 nmol mg(-1) protein) on isolated liver mitochondria decreased oxygen consumption of state 3 respiration, as well as DeltaPsi, but increased oxygen consumption of state 4 respiration, characteristic of an uncoupler effect. Analysis of segments of the respiratory chain suggested that the TRN inhibition site is located between complexes II and III. Mitochondrial swelling, energized or driven by the K+ diffusion potential using valinomycin, was also inhibited by TRN, the former being completely inhibited at concentrations greater than 10 nmol TRN mg(-1) protein, suggesting that it is also able to interfere with fluidity of the inner mitochondrial membrane. These results suggest that, besides its antibacterial effect, TRN can also impair the mitochondrial function of animal cells.     

Effect of a novel thromboxane A2 synthetase inhibitor on ischemia-induced mitochondrial dysfunction in canine hearts

This study was designed to determine the effect of sodium 6-(2-[1-(1H)-imidazolyl]methyl-4,5-dihydrobenzo[b] thiophene)carboxylate (RS-5186), a new thromboxane A2 (TXA2) synthetase inhibitor, on mitochondrial function and lysosomal integrity in ischemic myocardium. 17 anesthetized mongrel dogs were divided into 2 groups. In the control group (n = 11), the left anterior descending arteries (LAD) of the dogs were occluded for 2 h and physiological saline was infused until the end of the experiment. In the RS-5186 treated group (n = 6), 25 min prior to LAD occlusion, RS-5186, 10 mg/kg, was injected for 10 min. 2 h after occlusion, mitochondria were prepared from both ischemic and non-ischemic areas, which were confirmed by Evans' blue dye, and mitochondrial function (respiratory control index: RCI, and the rate of oxygen consumption in state III respiration: St.III O2) was measured polarographically with succinate as substrate. Fractionation of myocardial tissue from both ischemic and non-ischemic areas was also performed, and the activities of lysosomal enzymes (N-acetyl-beta-glucosaminidase: NAG, beta-glucuronidase: beta-gluc) of each fraction were measured. 2-h LAD occlusion induced a significant greater decrease in mitochondrial function from the ischemic area of the control group (RCI: 2.80 +/- 0.45, St.III O2: 133.5 +/- 35.6 natoms/mg protein/min) compared with those from the non-ischemic area (RCI: 4.49 +/- 0.46, St.III O2: 344.0 +/- 31.9).(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibition of mitochondrial respiration in vivo is an early event in acetaminophen-induced hepatotoxicity

Morphological changes in mitochondria are observed early in the course of acetaminophen (AA)-induced hepatotoxicity, and mitochondrial dysfunction has been observed both in vivo and in vitro following exposure to AA. This study examined the early effects of AA exposure in vivo on mitochondrial respiration and evaluated the effectiveness ofN-acetyl-L-cysteine (NAC) in protecting against respiratory dysfunction. Mitochondria were isolated from the livers of fasted, male CD-1 mice 0, 0.5, 1, 1.5 or 2 h after administration of a hepatotoxic dose of AA (750 mg/kg). Glutamate- and succinate-supported mitochondrial respiration were subsequently assessed by polarographic measurement of state 3 (ADP-stimulated) and state 4 (resting) rates of oxygen consumption and determination of the corresponding respiratory control ratios (RCR: state 3/state 4) and ADP:O ratios. Hepatotoxicity was assessed histologically and by measuring plasma alanine aminotransferase (ALT) activity. The earliest sign of mitochondrial dysfunction observed in this study was a significant decrease in the ADP:O ratio for the oxidation of glutamate 1 h post-dosing. At 1.5 and 2 h post-dosing the RCRs for both glutamate- and succinate-supported respiration were significantly decreased. All of the respiratory parameters measured in this study were significantly decreased, with the exception of succinate-supported state 4 respiration which was significantly increased, 2 h after AA administration. Thus, inhibition of mitochondrial respiration preceded overt hepatic necrosis, indicated by an elevation of ALT activity, which was not observed until 3 and 4 h post-dosing. In addition, mitochondrial respiratory dysfunction correlated with morphological alterations. Inhibition of mitochondrial respiration therefore appears to be an early event in the course of AA-induced hepatotoxicity. Cotreatment with NAC (1200 mg/kg) completely prevented the AA-induced impairment of mitochondrial respiration and the development of histopathologic damage. The protection afforded by NAC in these experiments indicates thatN-acetyl-p-benzoquinone imine (NAPQI), the reactive metabolite of AA, is responsible for the observed inhibitory effects, and suggests that mitochondrial dysfunction makes an important, if not essential, contribution to the development of AA-induced hepatotoxicity.     

银杏内酯的快速测定方法的研究

目的：介绍一种快速测定银杏内酯的新方法。方法：采用单柱层析和高效液相色谱联用的化分离技术。结果和结论：该方法可减少样品的预纯化时间,与目前的常规测定方法相比,其纯化时间缩短到常规方法的１／６,回收率高,相对标准偏差小,而且操作简便,易于掌握,可用于银杏叶及其提取物（ＧＢＥ）中银杏内酯的快速测定和质量监控。     

银杏叶提取物抗鼠肾缺血再灌注损伤及对P选择素表达的影响

目的 :探讨银杏叶提取物保护大鼠肾脏缺血再灌注损伤作用与机理。方法 :SD大鼠随机分为假手术组、缺血再灌注组、银杏叶提取物组。通过HE染色观察肾组织损伤和中性粒细胞浸润 ,免疫组织化学方法观察P选择素的表达情况。结果 :与假手术组相比 ,缺血再灌注组肾小管上皮细胞呈明显的缺血性改变 ,P选择素表达明显增强 (P <0 .0 1) ,肾小球内中性粒细胞增加明显 (P <0 .0 0 1) ;银杏叶提取物组比缺血再灌注组肾小管上皮细胞缺血性改变减轻 ,P选择素表达减少 (P <0 .0 1) ,肾小球内中性粒细胞较缺血再灌注组减少 (P <0 .0 0 1)。结论 :银杏叶提取物减轻大鼠肾缺血再灌注损伤 ,减少P选择素表达及中性粒细胞浸润     

Influence of ethanol extract of Ginkgo biloba leaves on the isolated rat heart work and mitochondria functions

In this study, we attempted to elucidate whether the effects of ethanol extract of Ginkgo biloba leaves (GBE) observed previously on isolated rat heart mitochondria may be realized in situ (in case of isolated heart perfused under normal conditions and under ischemia-reperfusion). We found that GBE at low concentrations (0.01, 0.05, and 0.1 μL/mL) does not affect the heart rate and parameters of electrocardiogram (ECG) but produces a small increase in the coronary flow. Higher concentration of GBE (0.2 and 0.3 μL/mL) diminished the heart rate, decreased the coronary flow, and tended to enhance the parameters of ECG. The contractility of isolated rat heart and mitochondrial nicotinamide adenine dinucleotide reduced form fluorescence decreased in a GBE concentration-dependent manner. Mitochondria isolated from hearts pre-perfused with GBE (0.05 μL/mL) for 20 minutes before nonflow global ischemia-reperfusion (45 min/15 min) showed higher respiratory rates with pyruvate + malate in state 2 and state 3, higher respiratory control index, and diminished H?O? generation compared with untreated group. Higher GBE concentration, 0.4 μL/mL, had no effect on H2O2 generation and did not prevent the ischemia-reperfusion-induced decrease of pyruvate + malate oxidation in state 3 but even enhanced it. However, in the case of nonischemic perfusions, this GBE concentration had no significant effect on these parameters of respiratory functions of isolated heart mitochondria.     

Effects of guanethidine on electron transport and proton movements in rat heart, brain and liver mitochondria

Guanethidine at 5-25 mM concentrations was found to induce up to 79% inhibition of ADP-stimulated (state III) oxygen consumption in isolated rat heart, brain or liver mitochondria, when the added substrate was glutamate or succinate, but the inhibition was considerably lower (24% or less) when respiration was supported by ascorbate plus tetramethylphenylenediamine (TMPD). Comparable results were seen regarding ADP-stimulated proton uptake, where even greater inhibition (up to 94% with glutamate or succinate, but not ascorbate plus TMPD) was found. Similar but somewhat less marked effects were also seen in resting (state IV) respiration and on the acceptor control ratio (state III/state IV respiration). 2,4-Dinitrophenol was unable to relieve guanethidine-induced inhibition of electron transport. These results indicate that guanethidine inhibits primarily mitochondrial electron transport itself, and that the site where such inhibition is more marked is located in the span between ubiquinone and cytochrome c of the respiratory chain. It is, therefore, suggested that active guanethidine uptake by noradrenergic neurons can lead to a high drug concentration in their cytoplasm and hence to mitochondrial alterations that can contribute to the pharmacological effect of this drug. Our results demonstrate the interaction between guanethidine and the electron transport chain of mitochondria derived from different tissues and, therefore, support this hypothesis.     

Distinct role of bilobalide and ginkgolide A in the modulation of rat CYP2B1 and CYP3A23 gene expression by Ginkgo biloba extract in cultured hepatocytes.

In the present study, primary cultures of rat hepatocytes were treated for 48 h with one of several extracts of Ginkgo biloba (10, 100, or 1000 microg/ml). Maximal increase in CYP2B1 and CYP3A23 mRNA levels was obtained at 100 microg/ml. This concentration of G. biloba extract also increased CYP3A2 and CYP3A18 mRNA expression in addition to CYP2B-mediated 7-benzyloxyresorufin O-dealkylation (BROD) and CYP3A-mediated testosterone 6beta-hydroxylation. In other experiments, cultured hepatocytes were treated for 48 h with bilobalide, ginkgolide A, ginkgolide B, ginkgolide C, ginkgolide J, kaempferol, quercetin, isorhamnetin, or a flavonol diglycoside at a concentration that represented the level present in a 100 microg/ml concentration of an extract. Only bilobalide (2.8 microg/ml) increased CYP2B1 mRNA expression, and the -fold increase (7.9 +/- 0.5; mean +/- S.E.M.) was similar to that (8.3 +/- 1.7) by the extract. By comparison, only ginkgolide A (1.1 microg/ml) increased CYP3A23 mRNA expression, but the extent (2.6 +/- 0.5-fold) was less than the 5.3 +/- 1.7-fold increase by the extract. A greater concentration (5 microg/ml) of ginkgolide A was required to elevate CYP3A2 and CYP3A18 mRNA expression. Over the range of 1 to 5 microg/ml, bilobalide increased CYP2B1 mRNA and BROD, but not CYP3A23 mRNA or testosterone 6beta-hydroxylation, whereas ginkgolide A increased CYP3A23 mRNA and testosterone 6beta-hydroxylation, but not CYP2B1 mRNA or BROD. Overall, our novel results indicate a distinct role of bilobalide and ginkgolide A in the modulation of CYP2B1 and CYP3A23 gene expression and enzyme activities by G. biloba extract in primary cultures of rat hepatocytes.     

Inhibition and uncoupling of oxidative phosphorylation by nonsteroidal anti-inflammatory drugs: study in mitochondria, submitochondrial particles, cells, and whole heart

The effects of the anti-inflammatory drugs diclofenac, piroxicam, indomethacin, naproxen, nabumetone, nimesulide, and meloxicam on mitochondrial respiration, ATP synthesis, and membrane potential were determined. Except for nabumetone and naproxen, the other drugs stimulated basal and uncoupled respiration, inhibited ATP synthesis, and collapsed membrane potential in mitochondria incubated in the presence of either glutamate + malate or succinate. Plots of membrane potential versus ATP synthesis (or respiration) showed proportional variations in both parameters, induced by different concentrations of nimesulide, meloxicam, piroxicam, or indomethacin, but not by diclofenac. The activity of the adenine nucleotide translocase was blocked by diclofenac and nimesulide; diclofenac also slightly inhibited mitochondrial ATPase activity. Naproxen did not affect any of the mitochondrial parameters measured. Nabumetone inhibited respiration, ATP synthesis, and membrane potential in the presence of glutamate + malate, but not with succinate. NADH oxidation in submitochondrial particles also was inhibited by nabumetone. Nabumetone inhibited O2 uptake in intact cells and in whole heart, whereas the other five drugs stimulated respiration. These observations revealed that in situ mitochondria are an accessible target. Except for diclofenac, a negative inotropic effect on cardiac contractility was induced by the drugs. The data indicated that nimesulide, meloxicam, piroxicam, and indomethacin behaved as mitochondrial uncouplers, whereas nabumetone exerted a specific inhibition of site 1 of the respiratory chain. Diclofenac was an uncoupler too, but it also affected the adenine nucleotide translocase and the H+-ATPase.     

HPLC—ELSD法测定银杏叶中的4种萜类内酯含量

目的：用高效液相色谱－蒸发光散射检测法（HPLC－ELSD）直接测定银 杏叶中银杏萜类内酯A、B、C及白果内酯的含量。方法：银杏叶10％甲醇提取液通过聚酰胺及硅胶小柱联用净化制成供试品溶液,经C18色谱柱,以甲醇－水为流动相,梯度洗脱,以蒸发光检测器检测。结果：银杏叶供试品溶液的预处理是获得准确测定结果的关键,多点校正,自然对数换算以弥补ELSD线性应答差的不足。结论：测定不同产地、不同树龄、不同采收季节的银杏叶中萜类内酯含量,对从源头抓好原料质量有积极意义。