共查询到20条相似文献,搜索用时 46 毫秒
1.
1. Rat kidney mitochondria oxidize glutamate very slowly. Addition of glutamine stimulates this respiration two- to three-fold. Addition of glutamate also stimulates respiration in the presence of glutamine. 2. By measuring mitochondrial swelling in iso-osmotic solutions of glutamine or of ammonium glutamate it was shown that glutamine penetrates the mitochondrial membrane rapidly whereas ammonium glutamate penetrates very slowly. 3. Experiments in which reduction of NAD(P)+ was measured in preparations of intact and broken mitochondria indicated that glutamate dehydrogenase shows the phenomenon of `latency'. On the addition of glutamine rapid reduction of nicotinamide nucleotides in intact mitochondria was obtained. 4. During the action of glutaminase there is an accumulation of glutamate inside the mitochondria. 5. When the mitochondria were suspended in a medium containing glutamine, Pi and rotenone the rate of production of ammonia was stimulated by the addition of a substrate, e.g. succinate. Addition of an uncoupler or antimycin A abolished this stimulation. 6. The effects of succinate and uncoupler were especially pronounced in the presence of glutamate, which is an inhibitor of glutaminase activity by competition with Pi. 7. Determination of the enzyme activity in media at different pH values showed that the optimum pH for glutaminase activity in the preparation of broken mitochondria was 8, whereas for intact mitochondria it was dependent on the energy state. In the presence of succinate as an energy source it was pH 8.5, but in the presence of uncoupler or antimycin A it was 9. This displacement of the pH optimum to a higher value was especially pronounced in the presence of both glutamate and uncoupler. 8. If nigericin was present in potassium chloride medium the pH optimum for enzyme activity in intact non-respiring mitochondria was nearly the same as in the preparation of broken mitochondria; however, its presence in K+-free medium displaced the pH optimum for glutaminase activity to a very high value. 9. It is postulated that because of low permeability of the kidney mitochondrial membrane to glutamate the latter accumulates inside the mitochondria, and that this leads to the inhibition of the enzyme by competition with Pi and also by lowering the pH of the intramitochondrial space. With succinate as substrate for respiration there is an outward translocation of H+ ions, which together with accumulation of Pi increases glutaminase activity. Translocation of K+ ions inward increases the enzyme activity, perhaps by increasing the pH of the internal spaces and causing an accumulation of Pi. 10. The importance of the location of the enzyme in the mitochondria in relation to its biological function and conditions for activity is discussed. 相似文献
2.
Carlson DE Pumplin DW Ghavam S Fiedler SM Chiu WC Scalea TM 《Journal of bioenergetics and biomembranes》2005,37(5):327-339
Lung mitochondria were isolated by differential centrifugation from pentobarbital-anesthetized male rats. One to three millimolar
Mg2+-ATP increased the consumption of oxygen of lung mitochondria oxidizing 10 mM succinate > fourfold (P < 0.01) whereas ATP increased the respiration of liver mitochondria by < 35%. ATP also hyperpolarized partially uncoupled
lung mitochondria in the presence of the mitochondria-specific antagonist, oligomycin. However, only 20% of the ATPase activity
in the lung mitochondria was blocked by oligomycin compared to a blockade of 91% for liver mitochondria. We investigated the
effect of reducing the non-mitochondrial ATPase activity in the lung preparation. A purer suspension of lung mitochondria
from a Percoll gradient was inhibited 95% by oligomycin. The volume fraction identified as mitochondria by electron microscopy
in this suspension (73.6± 3.5%) did not differ from that for liver mitochondria (69.1± 4.9%). ATP reduced the mean area of
the mitochondrial profiles in this Percoll fraction by 15% (P <0.01) and increased its state 3 respiration with succinate as substrate by 1.5-fold (P < 0.01) with no change in the state 4 respiration measured after carboxyatractyloside. Hence, ATP increased the respiratory
control ratio (state 3/state 4, P <0.01). In contrast, state 3 respiration with the complex 1-selective substrates, glutamate and malate, did not change with
addition of ATP. The acceleration of respiration by ATP was accompanied by decreased production of H2O2. Thus ATP-dependent processes that increase respiration appear to improve lung mitochondrial function while minimizing the
release of reactive oxygen species. 相似文献
3.
After irradiation of rats with a linear electron accelerator, the respiratory rate in rat brain mitochondria was studied in the presence of substrate + ADP and after the conversion of ADP → ATP. After 20,000 rads of irradiation to the head there was a transient diminution of mitochondrial respiratory control when glutamate was used as the substrate, but no changes were observed when succinate was the substrate. Irradiation with 10,000 rads had no effect upon respiratory control. The addition of NADH2 to irradiated mitochondria had no effect upon mitochondrial respiration. Irradiation of the brain with 20,000 rads failed to produce mitochondrial peroxidation or swelling, even in the presence of FeNH4(SO4)2 or ascorbate. The slight changes in respiratory control of brain mitochondria following irradiation is in marked contrast to the susceptibility of mitochondria from other organs. The comparative radioresistance of brain mitochondria may be the result of greatly diminished radiation-induced peroxidation of cerebral mitochondrial membranes. 相似文献
4.
Mikhail Y. Syromyatnikov Artem P. Gureev Inna Y. Vitkalova Anatoly A. Starkov Vasily N. Popov 《Archives of insect biochemistry and physiology》2019,102(1)
Honey bees Apis mellifera L. are one of the most studied insect species due to their economic importance. The interest in studying honey bees chiefly stems from the recent rapid decrease in their world population, which has become a problem of food security. Nevertheless, there are no systemic studies on the properties of the mitochondria of honey bee flight muscles. We conducted a research of the mitochondria of the flight muscles of A. mellifera L. The influence of various organic substrates on mitochondrial respiration in the presence or absence of adenosine diphosphate (ADP) was investigated. We demonstrated that pyruvate is the optimal substrate for the coupled respiration. A combination of pyruvate and glutamate is required for the maximal respiration rate. We also show that succinate oxidation does not support the oxidative phosphorylation and the generation of membrane potential. We also studied the production of reactive oxygen species by isolated mitochondria. The greatest production of H2O2 (as a percentage of the rate of oxygen consumed) in the absence of ADP was observed during the respiration supported by α‐glycerophosphate, malate, and a combination of malate with another NAD‐linked substrate. We showed that honey bee flight muscle mitochondria are unable to uptake Ca2+‐ions. We also show that bee mitochondria are able to oxidize the respiration substrates effectively at the temperature of 50°С compared to Bombus terrestris mitochondria, which were more adapted to lower temperatures. 相似文献
5.
R. A. Khatypov A. M. Khristin T. Yu. Fufina V. A. Shuvalov 《Biochemistry. Biokhimii?a》2017,82(6):692-697
In the absorption spectrum of Rhodobacter sphaeroides reaction centers, a minor absorption band was found with a maximum at 1053 nm. The amplitude of this band is ~10,000 times less and its half-width is comparable to that of the long-wavelength absorption band of the primary electron donor P870. When the primary electron donor is excited by femtosecond light pulses at 870 nm, the absorption band at 1053 nm is increased manifold during the earliest stages of charge separation. The growth of this absorption band in difference absorption spectra precedes the appearance of stimulated emission at 935 nm and the appearance of the absorption band of anion-radical BA – at 1020 nm, reported earlier by several researchers. When reaction centers are illuminated with 1064 nm light, the absorption spectrum undergoes changes indicating reduction of the primary electron acceptor QA, with the primary electron donor P870 remaining neutral. These photoinduced absorption changes reflect the formation of the long-lived radical state PBAHAQA –. 相似文献
6.
Helminthosporium maydis Race T Toxin Induces Leakage of NAD from T Cytoplasm Corn Mitochondria 总被引:11,自引:5,他引:6
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The mechanism by which Helminthosporium maydis race T toxin inhibits respiration dependent on NAD+-linked substrates in T cytoplasm corn mitochondria was investigated. The toxin did not cause leakage of the soluble matrix enzyme malate dehydrogenase from the mitochondria or inhibit malate dehydrogenase or isocitrate dehydrogenase directly. The toxin did increase the permeability of the inner membranes of T cytoplasm, but not N cytoplasm, mitochondria to NAD+. Added NAD+ partially or fully restored toxin-inhibited electron transport in T cytoplasm mitochondria. Thiamin pyrophosphate had a similar effect when malate was the substrate. It was concluded that the inhibition of respiration of NAD+-linked substrates by the toxin is due to depletion of the intramitochondrial pool of NAD+ and other coenzymes. 相似文献
7.
The simultaneous determination of carbon dioxide release and oxygen uptake in suspensions of plant leaf mitochondria oxidizing glycine 总被引:2,自引:2,他引:0
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The construction and operation of a device for continuous measurement of CO2 release by suspensions of respiring mitochondria is described. A combination of this device with a Clark-type O2 electrode was used for simultaneous measurement of respiration and of CO2 release by spinach and pea leaf mitochondria with glycine as substrate. Both mitochondrial preparations showed high rates of respiration and high respiratory control ratios. The addition of oxaloacetate not only inhibited O2 uptake substantially, but also greatly stimulated glycine oxidation as monitored by CO2 release. In spinach leaf mitochondria, the maximal rates of glycine oxidation thus obtained, were two times higher than the rate of glycine oxidation required at average rates of photorespiration. It is concluded from these results that under saturating conditions the capacity of glycine oxidation by intact mitochondria exceeds the capacity of glycine-dependent respiration. 相似文献
8.
Results are presented of a study of primary processes of formation of the charge separated states P+BA
- and P+HA
- (where P is the primary electron donor, BA and HA the primary and secondary electron acceptors) in native and pheophytin-modified reaction centers (RCs) of Rhodobacter sphaeroides R-26 by methods of femtosecond spectroscopy of absorption changes at low temperature. Coherent oscillations were studied in the kinetics at 935 nm (P* stimulated emission band), at 1020 nm (BA
- absorption band), and at 760 nm (HA absorption band). It was found that when the wavepacket created under femtosecond light excitation approaches the intersection between P* and P+BA
- potential surfaces at 120- and 380-fsec delays, the formation of two electron states emitting light at 935 nm (P*) and absorbing light at 1020 nm (P+BA
-) takes place. At the later time the wavepacket motion has a frequency of 32 cm-1 and is accompanied by electron transfer from P* to BA in pheophytin-modified and native RCs and further to HA in native RCs. It was shown that electron transfer processes monitored by the 1020-nm absorption band development as well as by bleaching of 760-nm absorption band have the enhanced 32 cm-1 mode in the Fourier transform spectra. 相似文献
9.
The effect of trifluoperazine on the respiration of porcine liver and skeletal muscle mitochondria was investigated by polarographic and spectroscopic techniques. Low concentrations of trifluoperazine (88 nmol/mg protein) inhibited both the ADP- and Ca2+-stimulated oxidation of succinate, and reduced the values of the respiratory control index and the and ratio. High concentrations inhibited both succinate and ascorbate plus tetramethyl-p-phenylenediame (TMPD) oxidations, and uncoupler (carbonyl cyanide p-trifluromethoxyphenylhydrazone) and Ca2+-stimulated respiration. Porcine liver mitochondria were more sensitive to trifluoperazine than skeletal muscle mitochondria. Trifluoperazine inhibited the electron transport of succinate oxidation of skeletal muscle mitochondria within the cytochrome b-c1 and cytochrome c1-aa3 segments of the respiratory chain system. 233 nmol trifluoperazine/mg protein inhibited the aerobic steady-state reduction of cytochrome c1 by 92% with succinate as substrate, and of cytochrome c and cytochrome aa3 by 50–60% with ascorbate plus TMPD as electron donors. Trifluoperazine can thus inhibit calmodulin-independent reactions particularly when used at high concentrations. 相似文献
10.
Whole cell respiration rates were measured polarographically for Naegleria gruberi during growth in agitated cultures. Log growth phase amebae consumed 80 ng atoms O/min/mg cell protein. At stationary phase, respiration rate decreased 4–fold. Intact mitochondria were isolated from N. gruberi and their oxidative and phosphorylative capacities were studied polarographically. As with the mammalian system, the mitochondria oxidized succinate and NAD-linked substrates, but unlike rat liver mitochondria, those from the protozoan rapidly oxidized citrate and NADH. The rates of substrate oxidation were ADP-dependent, with ADP:O ratios equalling ? 2.8 for NAD-linked substrates and ? 2.2 for succinate. The respiratory control ratios. 2 to 4 for 11 substrates, were dependent on Pi, Mg2+, and serum albumin. Potassium cyanide, azide, malonale, and rotenone inhibited electron transport the same way as that of the mammalian system: however, amytal inhibited both glutamate and succinate respiration. Pentachlorophenol, DNP, and bilirubin uncoupled oxidation from phosphorylation. Difference spectra of oxidized and dithionite-reduced mitochondria had distinct absorption bands of flavins and of c-, b-, and α-type cytochromes. 相似文献
11.
We developed a computational model of mitochondrial energetics that includes Ca2+, proton, Na+, and phosphate dynamics. The model accounts for distinct respiratory fluxes from substrates of complex I and complex II, pH effects on equilibrium constants and enzyme kinetics, and the acid-base equilibrium distributions of energy intermediaries. We experimentally determined NADH and ΔΨm in guinea pig mitochondria during transitions from de-energized to energized, or during state 2/4 to state 3 respiration, or into hypoxia and uncoupling, and compared the results with those obtained in model simulations. The model quantitatively reproduces the experimentally observed magnitude of ΔΨm, the range of NADH levels, respiratory fluxes, and respiratory control ratio upon transitions elicited by sequential additions of substrate and ADP. Simulation results are also able to mimic the change in ΔΨm upon addition of phosphate to state 4 mitochondria, leading to matrix acidification and ΔΨm polarization. The steady-state behavior of the integrated mitochondrial model qualitatively simulates the dependence of respiration on the proton motive force, and the expected flux-force relationships existing between respiratory and ATP synthesis fluxes versus redox and phosphorylation potentials. This upgraded mitochondrial model provides what we believe are new opportunities for simulating mitochondrial physiological behavior during dysfunctional states involving changes in pH and ion dynamics. 相似文献
12.
This study correlates the decreasing aerobic metabolism with the increased deterioration of mitochondria in maturing reticulocytes. The respiration of reticulocytes, separated into four age groups according to their density, was determined manometrically. Their Krebs tricarboxylic acid cycle activity was determined using [2-14C] acetate as a substrate for [14C]CO2 formation. The ability of reticulocytes of various age groups to couple the phosphorylation to oxidation processes was estimated by studying the effect of 2,4-dinitrophenol as an uncoupler. 相似文献
13.
The equal rates of water vapour absorption by both bi- and trinucleate pollen indicate that their widely-differing rates of respiration have an intrinsic, biochemical basis. This was investigated with various metabolic inhibitors that were previously introduced into dry pollen via anhydrous acetone. The uncoupler, carbonyl cyanide m-chlorophenyl hydrazone, inhibited the O2 uptake of rapidly respiring pollen and stimulated that of slowly respiring types to similar absolute values, that probably reflect the rates of substrate transport across the mitochondrial membranes. The extent of inhibition of the O2 uptake by oligomycin, dicyclohexyl carbodiimide, antimycin A, and salicyl hydroxamic acid, alone and in combinations, indicates that hardly any oxidative phosphorylation and anabolic activities occur in slowly respiring, binucleate pollen species, having low-developed mitochondria and high energy charge values. The presence of the alternative pathway was insignificant. In other binucleate pollen species, characterized by recognizable mitochondria and low energy charge values, a limited ATP synthesis was established. The low energy charge values point to imbalance between phosphorylative and anabolic activities. In rapidly respiring, trinucleate pollen, containing well-developed mitochondria, a significant activity of the alternative oxidase was found. The energy charge values were high notwithstanding the large demand for ATP, mounting to 1.7 μmol h?1 (mg pollen)?1. In some pollen species, oligomycin highly stimulated the flow of electrons through the cytochrome pathway, which made an estimation of the ATP synthesis impossible. 相似文献
14.
Priscila R Moreira Marcos A Maioli Hyllana CD Medeiros Marieli Guelfi Flávia TV Pereira Fábio E Mingatto 《Biological research》2014,47(1)
Background
The liver is an important organ for its ability to transform xenobiotics, making the liver tissue a prime target for toxic substances. The carotenoid bixin present in annatto is an antioxidant that can protect cells and tissues against the deleterious effects of free radicals. In this study, we evaluated the protective effect of bixin on liver damage induced by carbon tetrachloride (CCl4) in rats.Results
The animals were divided into four groups with six rats in each group. CCl4 (0.125 mL kg-1 body wt.) was injected intraperitoneally, and bixin (5.0 mg kg-1 body wt.) was given by gavage 7 days before the CCl4 injection. Bixin prevented the liver damage caused by CCl4, as noted by the significant decrease in serum aminotransferases release. Bixin protected the liver against the oxidizing effects of CCl4 by preventing a decrease in glutathione reductase activity and the levels of reduced glutathione and NADPH. The peroxidation of membrane lipids and histopathological damage of the liver was significantly prevented by bixin treatment.Conclusion
Therefore, we can conclude that the protective effect of bixin against hepatotoxicity induced by CCl4 is related to the antioxidant activity of the compound. 相似文献15.
THE PENETRATION OF THE MEMBRANE OF BRAIN MITOCHONDRIA BY ANIONS 总被引:1,自引:0,他引:1
The permeability of the membrane of rat brain non-synaptosomal mitochondria, towards inorganic and substrate anions, was assessed by measuring the rate of swelling that occurred when mitochondria were suspended in an iso-osmotic solution of a permeant anion, in the presence of a permeant cation such as NH+4 or K+ in the presence or absence of valinomycin. In NH+4-phosphate swelling was higher than it was in KCI or K+-phosphate, which showed the prevalence of the mechanism of phosphate transport previously demonstrated in liver mitochondria. The entry of succinate and L-malate seemed to require the presence in the inner mitochondrial membrane of specific carriers. as previously postulated for liver mitochondria, but the rate of swelling of brain mitochondria was lower than that of liver organelles. In K+-succinate, in the presence of antimycin, added ATP induced swelling and this was attributable to the simultaneous permeation both of the anion and the cation. Fumarate did not penetrate into brain mitochondria. Practically no swelling was recorded in NH+4 or K+-citrate, which indicated that this anion penetrated poorly into the isolated brain mitochondria even in the presence of malate. Swelling occurred in NH+4-L-glutamate in the presence of rotenone, and the entry of this anion seemed to follow a gradient of concentration although the presence of a specific translocator in the inner mitochondrial membrane might be concerned. The entry of glutamate was independent of that of phosphate and N-ethylmaleimide appeared to be a specific inhibitor of this entry. Swelling in K+-L-glutamate, in the presence of rotenone, was enhanced by the addition of valinomycin or ATP but in the latter case when osmotic equilibrium was reached swelling was not reversed by oligomycin. In conclusion, the lesser extent of swelling of isolated brain mitochondria compared with liver mitochondria could be attributed to the heterogeneity of the populations of these organelles, each population possessing its own characteristics of membrane permeability. Observations of electron micrographs of brain mitochondria incubated in iso-osmotic substrate anions confirmed the heterogeneous rate of swelling of these particles. 相似文献
16.
Exogenous NAD Effects on Plant Mitochondria: A Reinvestigation of the Transhydrogenase Hypothesis 总被引:4,自引:4,他引:0
Addition of NAD+ to purified potato (Solanum tuberosum L.) mitochondria respiring α-ketoglutarate and malate in the presence of the electron transport inhibitor rotenone, stimulated O2 uptake. This stimulation was prevented by incubating mitochondria with N-4-azido-2-nitrophenyl-aminobutyryl-NAD+ (NAP4-NAD+), an inhibitor of NAD+ uptake, but not by 1 mm EGTA, an inhibitor of external NADH oxidation. NAD+-stimulated malate-cytochrome c reductase activity, and reduction of added NAD+ by intact mitochondria, could be duplicated by rupturing the mitochondria and adding a small quantity to the cuvette. The extent of external NAD+ reduction was correlated with the amount of extra mitochondrial malate dehydrogenase present. Malate oxidation by potato mitochondria depleted of endogenous NAD+ by storing on ice for 72 hours, was completely dependent on added NAD+, and the effect of NAD+ on these mitochondria was prevented by incubating them with NAP4-NAD+. External NAD+ reduction by these mitochondria was not affected by NAP4-NAD+. We conclude that all effects of exogenous NAD+ on plant mitochondrial respiration can be attributed to net uptake of the NAD+ into the matrix space. 相似文献
17.
Joyce Johnson Diwan 《The Journal of membrane biology》1985,84(2):165-171
Summary Rapid uptake of Ba2+ by respiring rat liver mitochondria is accompanied by a transient stimulation of respiration. Following accumulation of Ba2+, e.g. at a concentration of 120 nmol per mg protein, the mitochondria exhibit reduced rates of state 3 and uncoupler-stimulated respiration. ADP-stimulated respiration is inhibited at a lower concentration of Ba2+ than is required to affect uncoupler-stimulated respiration, suggesting a distinct effect of Ba2+ on mechanisms involved in synthesis of ATP. Ba2+, which has an ionic radius similar to that of K+, inhibits unidirectional K+ flux into respiring rat liver mitochondria. This effect on K+ influx is observable at concentrations of Ba2+, e.g. 23 to 37 nmol per mg protein, which cause no significant change in state 4 or uncoupler-stimulated respiration. The accumulated Ba2+ decreases the measuredV
max of K+ influx, while having little effect on the apparentK
m
for K+. The inhibition of K+ influx by Ba2+ is seen in the presence and absence of mersalyl, an activator of K+ influx. In contrast, under the conditions studied, Ba2+ has no apparent effet on the rate of unidirectional K+ efflux. These data are consistent with the idea that K+ may enter and leave mitochondria via spearate mechanisms. 相似文献
18.
Summary Rabbit bone marrow mitochondria isolated by differential centrifugation showed typical oxypolarographic tracings with glutamate oxidation with ADP:O ratio of 2.9. Similar results were obtained with liver mitochondria of the same animal. When marrow mitochondria were oxydizing a substrate such as glutamate, added MgCl2 markedly stimulated state-4 respiration giving a respiratory rate identical to that of state-3. In contrast, no Mg2+-stimulation was observed with liver mitochondria. Oligomycin completely blocked the stimulation by Mg2+ but further addition of 2,4-dinitrophenol reactivated the oxygen consumption by uncoupling. Further purification of marrow mitochondria by density gradient centrifugation in Percoll provided identical oxypolarographic results. Moreover, when marrow mitochondria were incubated without Mg2+, they showed a low ATPase activity that was stimulated by 2,4-dinitrophenol and blocked by oligomycin. The presence of Mg2+ in the incubation medium uncovered an additional ATPase activity which was resistant to oligomycin and apparently unaffected by 2,4-dinitrophenol. It is concluded that bone marrow mitochondria possess two types of ATPase activity distinguished on the basis of their reactivity with oligomycin, 2,4-dinitrophenol and Mg2+.Abbreviations EDTA
ethylenediamine tetraacetate
- DNP
2,4-dinitrophenol
- BSA
bovine serum albumin
- BMM
bone marrow mitochondria
- LM
liver mitochondria
- Oligo.
oligomycin
- Anti A
antimycin A
Howard Hughes Investigator. 相似文献
19.
The redox dye methylene blue (MB) is proven to have beneficial effects in various models of neurodegenerative diseases. Here we investigated the effects of MB (100 nM, 300 nM, and 1 μM) on key bioenergetic parameters and on H2O2 production/elimination in isolated guinea pig brain mitochondria under normal as well as respiration-impaired conditions. As measured by high-resolution Oxygraph the rate of resting oxygen consumption was increased, but the ADP-stimulated respiration was unaffected by MB with any of the substrates (glutamate malate, succinate, or α-glycerophosphate) used for supporting mitochondrial respiration. In mitochondria treated with inhibitors of complex I or complex III MB moderately but significantly increased the rate of ATP production, restored ΔΨm, and increased the rate of Ca2+ uptake. The effects of MB are consistent with transferring electrons from upstream components of the electron transport chain to cytochrome c, which is energetically favorable when the flow of electrons in the respiratory chain is compromised. On the other hand, MB significantly increased the production of H2O2 measured by Amplex UltraRed fluorimetry under all conditions, in resting, ATP-synthesizing, and respiration-impaired mitochondria, with each substrate combination supporting respiration. Furthermore, it also decreased the elimination of H2O2. Generation of H2O2 without superoxide formation, observed in the presence of MB, is interpreted as a result of reduction of molecular oxygen to H2O2 by the reduced MB. The elevated generation and impaired elimination of H2O2 should be considered for the overall oxidative state of mitochondria treated with MB. 相似文献
20.
I. V. Shemarova S. M. Korotkov V. P. Nesterov 《Journal of Evolutionary Biochemistry and Physiology》2011,47(4):360-365
The inotropic Cd2+ action on frog heart is studied with taking into account its toxic effects upon mitochondria. Cd2+ at concentrations of 1, 10, and 20 mM is established to decrease dose dependently (21.3, 50.3, and 72.0%, respectively) the
muscle contraction amplitude; this is explained by its competitive action on the potential-controlled Na2+-channels of the L-type (Cav 1.2). In parallel experiments on isolated rat heart mitochondria (RHM) it was shown that Cd2+ at concentrations of 15 and 25 mM produces swelling of non-energized and energized mitochondria in isotonic (with KNO2 and NH2NO3) and hypoosmotic (with 25 mM CH3COOK) media. Study of oxidative processes in RHM by polarographic method has shown 20 mM Cd2+ to disturb activity of respiratory mitochondrial chain. The rate of endogenous respiration of isolated mitochondria in the
medium with Cd2+ in the presence of malate and succinate was approximately 5 times lower than in control. In experimental preparations, addition
into the medium of DNP—uncoupler of oxidation and phosphorylation did not cause an increase of the oxygen consumption rate.
Thus, the obtained data indicate that a decrease in the cardiac muscle contractility caused by Cd2+ is due not only to its direct blocking action on Ca2+-channels, but also is mediated by toxic effect on rat heart mitochondria, which was manifested as an increase in ion permeability
of the inner mitochondrial membrane (IMM), acceleration of the energy-dependent K+ transport into the matrix of mitochondria, and inhibition of their respiratory chain. 相似文献