镉与离体大鼠肾微粒体膜的相互作用

本文利用荧光探剂ANS研究了Cd~(2+)与大鼠肾微粒体膜的相互作用。结果发现,Cd~(2+)能明显增加与膜结合的ANS荧光强度和荧光偏振度。用ANS荧光滴定法研究证实Cd~(2+)能降低膜ANS复合物的表观解离常数(Kd)和增加膜上ANS的结合位点数(n)。上述结果提示,Cd~(2+)能降低大鼠肾微粒体膜流动性和膜表面负电荷密度。     

铅对发育中的脑脂质过氧化作用的影响

新生大鼠吸吮饮用含Pb~(2+)300 ppm和1000ppm水的母鼠乳汁(约含Pb~(2+)10～25ppm)连续21 d后,血铅和脑铅含量有显著增高,其血和脑ALAD活性亦有不同程度的抑制,说明Pb~(2+)容易由母体乳汁传递给新生大鼠引起铅中毒。另外还看到,新生大鼠脑匀浆、脑线粒体和微粒体的膜MDA含量及脂质过氧化荧光物质量比对照明显增加,血浆SOD活性抑制,均提示Pb~(2+)引起膜损伤(一是促进膜脂质过氧化作用;二是抑制SOD活性),因而出现Pb~(2+)对中枢神经系统的神经毒性。     

四氯化碳体外与大鼠肝微粒体膜作用的研究

向大鼠肝微粒体膜悬液中加入CCl_4(0.05～1μl/ml),可致膜脂过氧化和膜脂流动性降低。二巯基苏糖醇(DTT)和普鲁卡因能拮抗上述效应。CCl_4与微粒体膜作用后,ANS荧光强度降低并出现红移。结果提示,CCl_4诱发的膜脂过氧化可致微粒体膜的物理状态发生改变。     

绞股蓝总皂甙对离体大鼠肝脏脂质过氧化及膜流动性损伤的保护作用

在体外实验中绞股篮总皂甙(GP)能抑制大鼠肝微粒体自发的和由Fe_-~(2+)-半胱氨酸、Vit C-NADPH和CCl_4诱发的脂质过氧化,其作用强于人参总皂甙。Fe_-~(2+)-半胱氨酸导致大鼠肝微粒体、线粒体膜流动性降低,同时加入GP可防止膜流动性的下降。     

苯巴比妥诱导下大鼠肝微粒体药酶活性与膜流动性变化的相关性

本文用ANS和DPH为荧光探剂,研究苯巴比妥(PB)诱导下大鼠肝微粒体膜脂区流动性与膜药酶活性变化的相关性。结果表明,经PB诱导后在增加肝微粒体蛋白质含量,P-450含量及NADPH-细胞色素C还原酶等酶活性的同时,肝微粒体膜流动性明显增大,且膜深层流动性的增大与膜氨基比林N-脱甲基酶、细胞色素C还原酶活性增加有明显的直线正相关。膜胆固醇/碑脂比值明显降低。此结果提示,肝微粒体膜流动性的适当增大与PB增加单胺氧化酶系统活性之间可能存在着某种联系。     

苯巴比妥诱导下大鼠肝微粒体药酶活性与膜流动性变化的相关性

本文用ANS和DPH为荧光探剂,研究苯巴比妥(PB)诱导下大鼠肝微粒体膜脂区流动性与膜药酶活性变化的相关性。结果表明,经PB诱导后在增加肝微粒体蛋白质含量,P-450含量及NADPH-细胞色素C还原酶等酶活性的同时,肝微粒体膜流动性明显增大,且膜深层流动性的增大与膜氨基比林N-脱甲基酶、细胞色素C还原酶活性增加有明显的直线正相关。膜胆固醇/碑脂比值明显降低。此结果提示,肝微粒体膜流动性的适当增大与PB增加单胺氧化酶系统活性之间可能存在着某种联系。     

铅、镉对微粒体谷胱甘肽转移酶抑制机理的探讨

在纯化大鼠肝脏微粒体谷胱甘肽转移酶的基础上,我们研究了铅、镉在体外条件下,对纯化酶的影响,并初步探讨了影响机理。 结果表明,Pb~(2+)、Cd~(2+)对微粒体谷胱甘肽转移酶有明显的抑制作用,存在剂量效应、时间效应关系。按动力学方法鉴别Pb~(2+)、Cd~(2+)对纯化酶抑     

利用ANS为探剂研究溴氰菊酯和杀灭菊酯与突触体膜的相互作用

利用ANS为荧光探剂研究了溴氰菊酯和杀灭菊酯对突触体膜表面性质的影响。这两种带α-氰基的Ⅱ亚型拟除虫菊酯杀虫剂均可进一步增强ANS-突触体膜复合物的荧光强度。双倒数作图分析表明,这一效应是由于膜上ANS 的结合量增加,而不是ANS 的荧光量子产率改变所致。通过Scatchard作图分析测知ANS-突触体膜复合物的结合常数(n,Kd),发现这两种化合物可增加突触体膜对ANS 的结合容量和亲和力,这是膜表面负电荷密度降低的结果。这一效应与溴氰菊酯和杀灭菊酯对膜脂流动性的影响是相关的。     

胸腺因子D对老年大鼠肝微粒体,线粒体钙离子转运的影响

应用~(45)Ca研究了胸腺因子D(TFD)对老年大鼠肝脏亚细胞结构Ca~(2+)转运的影响,结果表明,与成年对照鼠(7月龄)相比,雄性老年大鼠(24月龄)肝微粒体,线枉体膜Ca(2+)主动摄取能力降低,肝微粒体Ca(2+)被动释放增多,给老年大鼠TFD 2 mg·kg~(-1)sc隔日一次共3月,可使其肝微枉体Ca(2+)主动摄取能力提高,Ca(2+)被动释放减少,有利于维持细胞内钙穗态,同时TFD还可逆转老年大鼠肝微粒体,线粒体膜流动性的降低及过氧化脂质的增高。     

两型拟除虫菊酯类杀虫剂对突触体膜流动性影响的研究

本研究利用荧光探剂DPH和ANS观察了六种根除虫菊酯类杀虫剂对大鼠脑突触体膜流动性的影响。发现带有α-氰基的拟除虫菊酯能降低突触体膜的流动性,且能增加脂双层极性头部的活动程度;而无α-氰基的拟除虫菊酯能增加突触体膜的流动性,但对脂双层极性头部的活动程度无明显影响。这六种杀虫剂对膜流动性的影响均发生在短时间内。     

Uptake of inorganic lead in vitro by isolated mitochondria and tissue slices of rat renal cortex

Slices of rat renal cortex were shown to take up Pb2+ during incubation in vitro; Pb2+ was also shown to enter mitochondria within the slices. The uptake of Pb2+ by isolated mitochondria was inhibited by N-3, La3+ and ruthenium red. A steady state of uptake was attained within 60 sec. The concentration dependence of uptake was complex; maximum uptake was attained at 25 microM and inhibition ensued at higher concentrations. A substantial inhibitor-resistant component of Pb2+ uptake was noted, especially at medium Pb2+ concentrations greater than 25 microM, and these concentrations also inhibited respiration state 3. The effects on respiration were reduced if the mitochondria had been preincubated with ruthenium red. Slices of renal cortex incubated at 1 degree in medium with various concentrations of Pb2+ showed two fractions of uptake, one saturating at 50-100 microM external Pb2+ and the other at 150-200 microM. Subsequent incubation for 60 min at 25 degrees led to further uptake at all concentrations. Upon isolation of mitochondria from incubated slices, significant amounts of Pb2+ were detected in the mitochondria within 5 min of addition of Pb2+ (200 microM), with maximum attained at 30 min. Electron microscopy of slices showed electron-dense particles, apparently of Pb2+, in the cortical cells but the greatest concentration was deposited in the basement membranes. The results indicate the importance of the basement membrane in limiting access of Pb2+ to cortical cells, and of mitochondria in accumulating Pb2+ once it is in the cells. They also illustrate the importance of interactions between Pb2+ and Ca2+.     

川芎嗪对兔血小板膜流动性、电泳迁移率的影响及其与抗凝作用的关系

已有报道,川芎嗪是川芎有效成分之一,对其结构已进行了鉴定。实验证明,川芎嗪有抑制血管平滑肌痉挛、改善急性心肌缺血等作用,并能抑制血小板聚集、降低血小板活性。但对于抑制聚集的机理特别是对血小板膜的作用未见报道。因此本实验研究川芎嗪对兔血小板膜流动性、电泳迁移率的影响及其与抗凝作用的关系,并初步探讨以上作用与血小板膜上生理过程的联系。     

INTERACTION OF SOME DRUGS, METAL IONS, AND ALCOHOLS WITH RAT LIVER MICROSOMES AS STUDIED WITH A FLUORESCENT PROBE

SUMMARY 1. The effects of various compounds on the fluorescence of microsome-bound 1-anilino-8-naphthalene sulphonate (ANS) have been studied.
2. Cationic drugs and divalent metal cations enhance the fluorescence of microsome-bound ANS whereas anionic drugs and primary aliphatic alcohols decrease it.
3. No changes were observed in the fluorescence lifetime or emission maximum of ANS and it was concluded that there were no significant changes in the quantum yield of ANS fluorescence.
4. The changes in fluorescence are shown to be related to changes in ANS binding.
5. The results suggest that drug-induced changes in the binding of ANS to the microsomal membrane reflect a change in the net charge on the membrane as a result of the binding of a charged drug and that changes in ANS fluorescence cannot be directly interpreted as changes in the structure of the membrane.
6. Primary aliphatic alcohols displace ANS from the microsomal membrane but cause no change in quantum yield. It is suggested that the alcohols change the net charge on the membrane either by exposure of negative charges or occlusion of positive charges.
7. The changes in ANS fluorescence can be used as a measure of the interaction of various drugs with the microsomal membrane. Apparent binding constants determined by this method for various drugs fall in the concentration ranges over which the drugs are reported to induce changes in membrane function in various in vitro systems.     

PbCl2-induced hyperpolarization of rat thymocytes: involvement of charybdotoxin-sensitive K+ channels

The effect of PbCl2 on membrane potential and intracellular divalent metal cation concentrations of rat thymocytes was examined by flow cytometry. PbCl2 at concentrations of 0.3 microM or higher (up to 10 microM) produced persistent, dose-dependent hyperpolarization (decrease in the intensity of di-BA-C4 fluorescence). Removal of external Ca2+ did not significantly affect the PbCl2-induced hyperpolarization. Charybdotoxin, a specific antagonist of Ca(2+)-dependent K+ conductance, greatly attenuated the PbCl2-induced hyperpolarization. PbCl2 increased the intensity of fluo-3 fluorescence under both normal Ca2+ and nominally Ca(2+)-free conditions. These results suggest that Pb2+ enters thymocytes, causing an increase in fluo-3 fluorescence, and activates Ca(2+)-dependent K+ channels, resulting in hyperpolarization. The persistent activation of K+ channels by Pb2+, leading to persistent hyperpolarization, may be one mechanism whereby Pb2+ alters immune function, as membrane potential changes influence physiological functions of lymphocytes.     

Effects of blowing sand fine particles on plasma membrane permeability and fluidity, and intracellular calcium levels of rat alveolar macrophages

Ambient fine particulate matter (PM2.5, particulates with an aerodynamic diameter < or = 2.5 microm) can suppress alveolar macrophage (AM) functions, but the data concerning the effects of blowing sand PM2.5 on AMs remain limited. The aim of the present study is to investigate the influences of blowing sand PM2.5 on AM plasma membranes and intracellular calcium ion concentration ([Ca2+]i), and explore the mechanisms of the observed toxicological effects. The samples of normal PM2.5 (collected on sunshiny and non-blowing sand days) and blowing sand PM2.5 were collected in Wuwei city, Gansu Province, China. After AMs from rat bronchoalveolar lavage fluid (BALF) were treated in vitro for 4 h with the suspensions of these samples, the cell viability, plasma membrane permeability and fluidity, cytosolic free Ca2+ levels, and oxidative stress were examined. It was observed a dose-dependent decrease in cell viability, plasma membrane Ca2+Mg2+-dependent adenosinetriphosphatase (Ca2+Mg2+-ATPase) and Na+K+-dependent adenosinetriphosphatase (Na+K+-ATPase) activities, cellular glutathione (GSH) levels, fluorescence intensities of lipid probe 8-anilino-1-naphthalene-sulfonic acid (ANS) and fluorescence polarization of lipid probe 1,6-diphenyl-1,3,5-hexatriene (DPH) combined with cell membranes in the treatment groups of normal and blowing sand PM2.5 as compared to the control (saline group); and also observed a dose-dependent increase in the leakage of lactate dehydrogenase (LDH) and acid phosphatase (ACP), and intracellular [Ca2+]i and malondialdehyde (MDA) levels. These observations indicate blowing sand PM2.5, as similar to urban normal ones, could induce oxidative stress on AMs, enlarge plasma membrane permeability and membrane lipid fluidity, and elevate intracellular [Ca2+]i levels, resulting in cytotoxicity. A two-way ANOVA showed the toxic effects of normal and blowing sand PM2.5 on AMs were only relative to treatment dosages but not to dust types, suggesting the blowing sand PM2.5 whose airborne mass concentrations were much higher should be more harmful.     

Permeabilization of E. coli K12 inner and outer membranes by bothropstoxin-I, A LYS49 phospholipase A2 from Bothrops jararacussu.

Although lacking catalytic activity, the Lys49-PLA(2)s damage artificial membranes by a Ca(2+)-independent mechanism, and demonstrate a potent bactericidal effect. The relationship between the membrane-damaging activity and bactericidal effect of bothropstoxin-I (BthTx-I), a Lys49-PLA(2) from the venom of Bothrops jararacussu, was evaluated for the wild-type protein and a series of site-directed mutants in the active site and C-terminal regions of the protein. The membrane permeabilization effect against the inner and outer membranes of Escherichia coli K12 was evaluated by fluorescence changes of Sytox Green and N-phenyl-N-naphthylamine, respectively. With the exception of H48Q, all mutants reduced the bactericidal activity, which correlated with a reduction of the permeabilization effect both against the inner bacterial membrane. No significant differences in the permeabilization of the bacterial outer membrane were observed between the native, wild-type recombinant and mutant proteins. These results suggest different permeabilization mechanisms against the inner and outer bacterial membranes. Furthermore, the structural determinants of bacterial inner membrane damage identified in this study correlate with those previously observed for artificial membrane permeabilization, suggesting that a common mechanism of membrane damage underlies the two effects.     

In vivo effects of psychotropic agents on the physical properties of cell membranes in the rat brain

Marked changes in biophysical properties, including structural order, have been observed in the hydrophobic core of cell membranes exposed to phenothiazines in vitro. In this study, similar changes are reported in vivo in cell membranes from the brains of rats treated with phenothiazines at doses thought to yield tissue concentrations approximating those attained in the clinical treatment of psychiatric patients. The membrane structural order parameter was estimated ex vivo by steady-state fluorescence polarization determinations using 1,6-diphenyl 1,3,5-hexatriene (DPH), a fluorescent probe that localizes preferentially to the hydrocarbon region of cell membranes. In these preliminary studies, rats received chlorpromazine (20 mg/kg), fluphenazine (1 mg/kg), haloperidol (1 mg/kg), and imipramine (1 mg/kg) in single or multiple dose protocols. As in earlier in vitro studies, exposure to the phenothiazine antipsychotics led to an observed increase in DPH fluorescence polarization ex vivo and a presumed increase in structural order. As predicted from the in vitro experiments, the effect of chlorpromazine was greater than that of fluphenazine, probably because chlorpromazine was given at higher doses. The magnitude of the effects seen was great enough to imply that physiologically significant changes in cell membrane characteristics may be produced in patients receiving phenothiazines.     

Binding of the membrane active drugs to bovine serum albumin and human erythrocyte membranes.

The binding of 14 non-steroidal anti-inflammatory drugs, 3 beta-adrenolytics and 8 miscellaneous drugs to bovine serum albumin (BSA) and human erythrocyte membranes (HEM) was investigated by using 8-anilino-1-naphthalene sulphonate (ANS) as a fluorescent probe. Anionic drugs which are known to protect proteins against denaturation strongly quench the fluorescence of the ANS-BSA complex, and to a lesser extent the fluorescence of the ANS-HEM complex. None of cationic or nonionic drugs tested so far are able to displace ANS from the ANS-BSA complex but some of them, known as “membrane active” agents, intensify the fluorescence of the ANS—HEM complex. Within the group of nonsteroidal anti-inflammatory drugs only those drugs which are inhibitors of prostaglandin biosynthesis have been found to quench the fluorescence of the complexes of ANS with BSA or HEM. Both anionic and cationic “membrane active” drugs protect erythrocytes against hypotonic hemolysis but the mechanisms of this effect are different.     

Biphasic changes in rat brain mitochondrial membrane structure and enzyme activity after acute opiate administration to rats

Results from experiments performed previously in our laboratory have shown that. subsequent to the administration of 25 mg of morphine/kg of rat, the phase transition of brain mitochondrial membrane lipids is altered. In the present work, Arrhenius plots were generated from the activity of three brain mitochondrial inner membrane-bound enzyme systems, in order to determine what changes in activity and activation energy (Ea) occurred after administration of a similar acute dose of morphine. Similar studies were carried out with mitochondrial matrix enzymes. Brain mitochondria were selected because the low membrane cholesterol content enables demonstration of an endothermic phase transition in the membrane lipids. Only the membrane-bound enzymes from mitochondria harvested 0.5 hr after morphine treatment in vivo had decreased activities. Simultaneously, the temperature of discontinuity of Arrhenius plots of state 4 succinoxidase and cytochrome oxidase was abolished, as was the higher of the two discontinuities in slate 3 succinoxidase; that of Mg²⁺ ATPase was decreased. When Arrhenius plots were generated with mitochondria harvested 48 hr after morphine administration, there was an increase in the activity of the succinoxidase and cytochrome oxidase systems, and their respective normal temperatures of discontinuity were abolished. With Mg²⁺ -stimulated ATPase. there was (1) an increase in the temperature of discontinuity and (2) the slopes of the activity curves differed markedly from the controls. Such effects were not obtained with the matrix enzymes 0.5 hr post opiate. When brain mitochondrial membranes harvested from rats 0.5 hr after opiate administration were incubated with 1-anilino-8-naphthalene sulfonic acid (ANS), there was a 15 per cent decrease (P < 0.05) in the fluorescence produced, compared with controls. This effect was abolished on treating the animals with either of the narcotic antagonists, oxilorphan (BC 2605A) or naloxone, 15 min after opiate administration. Brain mitochondria harvested 72 hr after acute morphine had a 22 per cent increase in fluorescnece on incubation with ANS (P < 0.005). These biphasic changes in both the activity and Ea of the membrane-bound enzymes, as well as the observed alteration in ANS fluorescence, were probably brought about by some type of morphine-induced change in the inner membrane of the mitochondria; they were entirely dependent on the time of sampling after opiate treatment. The probable role of concomitant changes in membrane lipid fluidity in these biphasic effects is advanced.