Inhibition of respiration by phenacetin in isolated tubules and mitochondria of rat kidney

Phenacetin. an analgesic drug thought to exert nephrotoxic effects in vivo, was found to inhibit respiration in isolated rat kidney tubules metabolizing endogenous substrate or exogenous glutamine, glucose or lactate. With isolated rat kidney mitochondria the oxidation of glutamate or succinate was strongly inhibited by phenacetin; in each case State 3 respiration and State 3u (uncoupled) respiration were affected to the same extent, indicating that phenacetin exerted its influence directly on the respiratory chain. The effects of phenacetin on the oxidation of NADH and succinate by submitochondrial particles in the presence of various electron acceptors suggested that at least two oxidoreduction reactions of the respiratory chain were susceptible to inhibition by phenacetin. One of these reactions was that catalysed by succinate dehydrogenase, while the other probably lay between reduced NADH dehydrogenase and coenzyme Q. The possibility that impairment to the oxygen-metabolising capacity of the kidney cell might contribute to the perceived cytotoxicity of phenacetin is discussed.     

二氮嗪对大鼠心肌线粒体膜电位及呼吸功能的影响

目的 :研究二氮嗪对大鼠心肌线粒体功能的影响 ,以探讨其心肌保护作用的可能机理。方法 :以罗丹明 12 3为荧光探针测定线粒体膜电位 ,氧电极法测线粒体呼吸 ,观察二氮嗪对正常大鼠心肌线粒体跨膜电位及呼吸的影响。结果 :5 0 μmol·L-1的二氮嗪可引起线粒体膜电位去极化 ,此影响可被钾通道阻滞剂消除 ;二氮嗪 10 0 μmol·L-1可降低大鼠心肌线粒体琥珀酸链的R3、R4速率 ,但不影响呼吸控制率。结论 :二氮嗪可调节大鼠心肌线粒体功能 ,这与其抗心肌缺血保护作用有关。     

Effects of streptonigrin derivatives and sakyomicin A on the respiration of isolated rat liver mitochondria

Though all the streptonigrin derivatives with modifications in the carboxyl group on C2' were active as electron acceptors in the oxidation of NADH by Clostridium kluyveri diaphorase as well as streptonigrin, the glycine derivative did not show any marked effect on the KCN-insensitive oxidation of glutamate by rat liver mitochondria, suggesting a poor membrane transport of the glycine derivative. Sakyomicin A also induced the KCN-insensitive oxidation of glutamate by mitochondria, while a trace activity was observed by mitomycin C and the effect of doxorubicin was negligible. Like streptonigrin, the autoxidation of a reduced form (hydroquinone) of sakyomicin A to a quinone accompanied the generation of H2O2. However, exogenous NADH was oxidized by mitochondria in the presence of sakyomicin A but not streptonigrin.     

吲哚美辛对大鼠和兔关节损伤的影响

AIM: To study the effects of indometacin (Ind) on joint damages. METHODS: The volume of noninjected hind paw and interleukin-1 (IL-1) production from peritoneal macrophages and articular synoviocytes induced by lipopolysaccharides were assayed in adjuvant arthritis (AA) rats. Measurements of synovial fibroblast proliferative response and proteoglycan synthesis of cartilage from rabbits were used. RESULTS: The secondary inflammatory reactions in AA rats on d 18, 21, and 24 were suppressed by i.g. Ind 2 mg.kg-1.d-1 for 9 d. Ind promoted IL-1 production from both macrophages and synoviocytes in AA rats. Ind 10 mumol.L-1 enhanced the proliferation of rabbit synovial fibroblasts and suppressed the proteoglycan synthesis of articular cartilage in response to IL-1 in vitro. CONCLUSION: Ind is unfavorable to the repair of joint destruction.     

Valproate-induced hyperammonemia of renal origin. Effects of valproate on glutamine transport in rat kidney mitochondria

The antiepileptic sodium valproate (VPA) systematically induces an asymptomatic hyperammonemia of renal origin in fasting normal human volunteers and in fasting rats, accompanied by an increased renal glutamine uptake. Fasting rats were injected with VPA and their mitochondria isolated, or isolated mitochondria of fasting rats were incubated with VPA. Transmembranal mitochondrial glutamine uptake and activities for five mitochondrial and three cytosolic enzymes involved in ammoniagenesis were measured. In VPA-incubated mitochondria, glutamine transport increased for VPA concentrations between 10(-3) and 10(-5) M; enzyme activities did not change. In mitochondria of VPA-treated rats, Km and Vmax were unaffected. These findings reflect membrane effects of VPA observed in other experimental settings.     

The effects of some nutritive antibiotics on the respiration of rat liver mitochondria.

(1) Seven antibiotics used as feed additives in animal breeding were investigated for their effects on isolated rat liver mitochondria. Three were found to interfere with mitochondrial energy metabolism. (2) Zinc-bacitracin completely inhibits mitochondrial respiration in the micromolar range. as do other inhibitors known to be highly effective against electron transport system. From studies of this antibiotic on the redox state of cytochromes, as measured by split beam spectra, it is concluded that the site of inhibition is located between cytochrome b and c₁ (antimycin A site). The effect is completely reversed by chelating agents, suggesting that Zn²⁺ ions are required for full activity of the cyclic peptide antibiotic. (3) Flavomycin, a polar glycolipid, linearly stimulates oxygen consumption of mitochondria under state 4 conditions in concentrations greater than 100 μmole/gram of protein. Lower concentrations of the antibiotic inhibits respiration of coupled as well as DNP- or FCCP-uncoupled mitochondria by about 70 per cent. While the uncouplinglike effect at high concentrations of the compound can be attributed to nonspecific surface activity which might facilitate proton conductance, the inhibitory activity seen at lower concentrations is assumed to be located near the second phosphorylation site of the respiratory chain. (4) The influence of chlortetracyclin (aureomycin) on mitochondrial activity was found to be dependent on the identity of the substrate. Succinate respiration was more sensitive to chlortetracyclin (CTC) addition by comparison with NAD-linked substrate oxidation. 45 μmole of CTC/gram of protein decreased succinate respiration to half maximal values, whereas glutamate plus malate or β-hydroxybutyrate respiration were inhibited by only 25 per cent. CTC partially inhibits the dehydrogenation of succinate by the succinate dehydrogenase. Uncoupling of oxidative phosphorylation completely abolished CTC-inhibited respiration of NAD-linked substrates, while succinate respiration remained inhibited by 25 per cent. The results of these experiments are discussed in terms of two sites of action for CTC, one located close to the phosphate carrier, while the second interferes with succinate dehydrogenase.     

Effects of anionic xenobiotics on rat kidney: I—tissue and mitochondrial respiration

The polar 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) metabolite, 2,2-bis p-chlorophenyl)acetic acid (DDA), and the phenoxyacetic acid herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), were previously shown to be accumulated to high levels in liver and kidney via the organic acid transport system, raising the possibility of organ-specific toxicity secondary to transport. In these studies, accumulation of DDA was shown to depress oxygen consumption by renal cortical slices at high doses (0.1 and 1 mM). Isolated renal and hepatic mitochondria were uncoupled by low doses of DDA (5–10 nmoles/mg mitochondrial protein). Maximal uncoupling was seen at 50–70 nmoles/mg. 2,4-D and 2,4,5-T also produced uncoupling, but at doses of 70 nmoles/mg or higher. All agents were more effective with α-ketoglutarate or pyruvatemalate as substrate than with succinate. With succinate as substrate (but not α-ketoglutarate or pyruvate-malate), all three agents also depressed State 3 (ADP-stimulated) respiration. Again. DDA was more effective than 2,4-D or 2,4,5-T. These results suggest that accumulation of these or other anionic xenobiotics may lead to toxicity in those tissues possessing the organic anion transport system.     

Multiple actions of phenylethylbiguanide on respiration by rat liver mitochondria

The effect of phenformin over a wide range of concentrations on oxidation of several subtrates by rat liver mitochondria was studied polarographically. Biphasic responses with both stimulatory and inhibitory phases were observed: their order of appearance depended on the nature of the substrate. Dose-response data for these phenomena are reported. At low phenformin concentrations (< 10^?4 M) only stimulation occurred, while at high concentrations (> 10^?2 M) only inhibition was observed. Insensitivity to dinitrophenol and ADP suggested that the stimulation was due to progressive uncoupling. Very high concentrations of phenformin did not inhibit the oxidation of ascorbate/TMPD. Possible sites of action of phenformin are discussed. Although it is not possible to define these with certainty it appears that several sites must be involved.     

Effects of the mycotoxin sporidesmin on swelling and respiration of liver mitochondria

In the presence of both oxidizable substrate and phosphate, low concentrations of sporidesmin produced rapid swelling of mitochondria isolated from guinea-pig liver. There is no requirement for alkali metal ions. Uncoupling agents or respiratory inhibitors inhibited the swelling. Mitochondria that had been swollen in the presence of sporidesmin could be contracted by addition of ATP, magnesium ions and bovine serum albumin. The rate of swelling was dependent on the concentration of both sporidesmin and mitochondrial protein and half-maximum effect was observed at 140 nmoles of sporidesmin per mg of protein. A lag period occurred before the maximal effect of sporidesmin and this period was also dependent on the concentration of both sporidesmin and mitochondrial protein. Sporidesmin decreased the respiratory control index of mitochondria by increasing the rate of state 4 respiration and decreasing that of state 3. As sporidesmin had no effect on the respiration of mitochondrial preparations that had either been treated with Triton X-100 or been subject to sonication, the toxin does not directly inhibit the respiratory chain. It is suggested that sporidesmin produces the effects described above by altering the permeability of the mitochondrial membrane.     

Effects of phenoperidine on rat liver mitochondrial respiration.

Phenoperidine decreases rat liver mitochondrial oxidation of the following substrates in state 3: glutamate, pyruvate/malate mixture, and succinate. The intensity of inhibition is dose-dependent and substrate-dependent. With glutamate which acts at the first phosphorylation site on the respiratory chain, phenoperidine seems to have two effects on mitochondrial oxidative processes: without preincubation, phenoperidine antagonizes mitochondrial oxidation of glutamate presumably by inhibiting enzymes involved in glutamate metabolism such as glutamate dehydrogenase and glutamate oxaloacetate transaminase. Upon a three min preincubation, an additional inhibitory mechanism develops: phenoperidine prevents glutamate from penetrating into the mitochondria. Inhibition without preincubation appears to be non competitive (K_i = 7.5 × 10^?5 M) and it is assumed that it takes place at a site before the 2,4-dinitrophenol (DNP)-sensitive site on the energy transfer process. In state 4, phenoperidine increases the oxidation of these substrates. It decreases the P/O ratio: thus it acts as an uncoupler, although not as potent as DNP. When compared with phenoperidine, levorphanol and pentazocine act as uncouplers but not as energy-transfer inhibitors. DALA-enkephalinamide increases state 4 respiration on glutamate. As for morphine, etorphine, meperidine and fentanyl, they do not act on mitochondrial processes. The effects of opiates on mitochondrial respiration are irrelevant to their morphinomimetic actions because they are not antagonized by naloxone.     

Studies on the ionophorous antibiotics. XII. Effects of ionophore lysocellin on cation distribution and respiration in mitochondria.

The effects of the ionophore lysocellin on the movements of Ca2+, Mg2+ and alkali metal cations and its effect on energy utilization by rat liver mitochondria have been investigated. At a concentration of 0.05 micrometer, lysocellin induced dissociation of membrane-bound calcium, and an apparent steady state was established across the inner membrane between energy-linked calcium accumulation and the ionophore-induced depletion of calcium. No detectable efflux of intramitochondrial Ca2+ and Mg2+ was induced by 0.05 micrometer lysocellin, but the uptake of exogenously added calcium was significantly inhibited. The ionophore augmented Mg2+ release from mitochondria induced by Ca2+ addition and also caused rapid release of K+ from mitochondria preloaded with K+ by valinomycin or monazomycin. High levels (0.5 approximately 10 micrometer of lysocellin caused massive depletion of endogenous Ca2+, Mg2+ and K+ from mitochondria, resulting in disruption of mitochondrial functions including release of state 4 respiration, stimulation of ATPase and inhibition of ADP- or DNP-stimulated respiration. Structure-activity studies with chemically modified compounds of lysocellin indicated the important role of terminal carboxylic acid and C21 hydroxyl function in the activity of the ionophore, and there is a good correlation between the effect of lysocellin on mitochondrial cation movements and its ability to complex with cations determined in an organic solvent-water two-phase partition system.     

Effects of aspirin, prednisolone and indomethacin on nephrotoxic serum nephritis in the rat.

1 The effects of aspirin, prednisolone, and indomethacin on nephrotoxic serum nephritis in rats was studied. The nephritis was induced by a single intravenous injection of nephrotoxic serum (NTS, rabbit anti-serum against the water-soluble renal antigen of the rat). The injection of NTS induced the heterologous phase of proteinuria (within a day after NTS injection) and then the autologous phase (5 to 7 days after NTS injection). The effect of drugs given before the NTS (i.e. prophylactically) or after the NTS (i.e. therapeutically) was investigated. 2 Aspirin, which was given orally at doses of 150 and 250 mg/kg daily from the day before NTS injection, suppressed the development of proteinuria in both the heterologous and the autologous phase, and lowered the serum cholesterol level towards the normal level. Aspirin (250 mg/kg daily, orally) had no significant effect against the established proteinuria in the autologous phase. 3 Prednisolone, which was given orally at doses of 3 and 5 mg/kg daily from the day before NTS injection, elevated the proteinuria in the heterologous phase, while inhibiting the development of proteinuria in the autologous phase. Prednisolone (5 mg/kg daily, orally) was ineffective against established proteinuria in the autologous phase. 5 Indomethacin (3 mg/kg daily, orally) did not exert any significant effect on proteinuria in either the heterologous or the autologous phase.     

Effects of ohmefentanyl on rat respiration

The respiratory depression in rats induced by sc ohmefentanyl showed a ceiling effect, but a linear relation with log dose when applied into the dorsal medulla. It elicited, however, a marked excitation on respiration when applied to dorsal pons. This excitatory effect of ohmefentanyl was antagonized by naloxone, and it antagonized to some extent the respiratory depressant effect induced by ohmefentanyl itself applied on dorsal medulla. It was postulated that the respiratory excitatory effect of sc ohmefentanyl on dorsal pons may have a bearing on the ceiling effect of its respiratory depression.     

Suramin inhibits respiration and induces membrane permeability transition in isolated rat liver mitochondria.

Suramin, a polysulfonated naphthylamine, caused a dose dependent inhibition of carbonyl cyanide p-(tri-fluoromethoxy)phenylhydrazone-stimulated respiration supported either by succinate or a cocktail of alphaketoglutarate, malate and isocitrate in isolated rat liver mitochondria. The half-maximum effect was obtained at 40 and 140 microM suramin for NADH- or FADH(2)-linked substrates, respectively. The respiration supported by N,N,N'N'-tetramethyl-p-phenylenediamine oxidation was unaffected by suramin (相似文献