Cephaloridine induces translocation of protein kinase C delta into mitochondria and enhances mitochondrial generation of free radicals in the kidney cortex of rats causing renal dysfunction

We have previously reported that the enhancement of free radical generation in mitochondria isolated from the kidney cortex of rats exposed to cephaloridine (CER) is probably mediated by the activation of protein kinase C (PKC). We examined which isoenzymes of PKC might be involved in the development of nephrotoxicity induced by CER in rats. The CER-induced renal dysfunction observed 24 h after its injection was prevented by a potent antioxidant DPPD and well-known PKC inhibitors like H-7 and rottlerin. At 1.5 and 3.5 h after the CER injection, the free radical generation was increased markedly and this was associated with translocation of PKCdelta into the mitochondria of renal cortex tissue. Pretreatment of rats with H-7, a PKC inhibitor, significantly inhibited the CER-derived increase in mitochondrial generation of free radicals, suggesting that H-7 probably gets into the mitochondria and inhibits the activity of translocated PKC within the mitochondria. It was also shown that pretreatment of rats with rottlerin, a specific inhibitor of PKCdelta, suppressed the early translocation of PKCdelta into mitochondria and inhibited the CER-derived development of renal dysfunction. These results suggest that the CER-derived early translocation of PKCdelta into mitochondria probably leads to the enhanced production of free radicals through the mitochondrial respiratory chain during the development of the nephrotoxicity caused by CER. Understanding the role of PKCdelta in mitochondria may provide an important clue to the molecular mechanisms of mitochondrial production of reactive oxygen species and the free radical-induced renal failure in rats treated with CER.     

Involvement of MEK/ERK pathway in cephaloridine-induced injury in rat renal cortical slices

We have previously reported that free radical-mediated injury induced by cephaloridine (CER) is enhanced by phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, in rat renal cortical slices. We have also shown that PKC activation in mitochondria is involved in CER-induced nephrotoxicity in rats. We investigated the role of a downstream PKC pathway, a MEK/ERK pathway, in free radical-induced injury in rat renal cortical slices exposed to CER. Immediately after preparing slices from rat renal cortex, the slices were incubated in the medium containing MEK inhibitors. ERK1/2 activation was determined by Western blot analysis for phosphorylated ERK (pERK) 1/2 protein in nucleus fraction prepared from the slices exposed to CER. Prominently, CER caused not only increases in lipid peroxidation as an index of free radical generation and in LDH leakage as that of cell injury in the slices, but also marked activation of ERK1/2 in nucleus fraction. PD98059 and U0126, MEK1/2 inhibitors, significantly attenuated CER-induced increases in lipid peroxidation and LDH leakage in the slices. PD98059 also suppressed ERK1/2 activation in nucleus fraction prepared from the slices treated with CER. Inhibition of other MAP kinase pathways, p38 MAP kinase and c-Jun N-terminal kinase (JNK) had no effect on CER-induced increases in lipid peroxidation level and LDH leakage in the slices. The present results suggest that a MEK/ERK pathway down stream of a PKC pathway is probably involved in free radical-induced injury in rat renal cortical slices exposed to CER.     

Protective effect of serum thymic factor, FTS, on cephaloridine-induced nephrotoxicity in rats

Serum thymic factor (FTS), a thymic peptide hormone, has been reported to increase superoxide disumutase (SOD) levels in senescence-accelerated mice. In the present study, we examined the effect of FTS on cephaloridine (CER)-induced nephrotoxicity in vivo and in vitro. We previously reported that CER led to extracellular signal-regulated protein kinase (ERK) activation in the rat kidney. So, we also investigated whether FTS has an effect on ERK activation induced by CER. Treatment of male Sprague-Dawley rats with intravenous CER (1.2 g/kg) for 24 h markedly increased BUN and plasma creatinine levels and urinary excretion of glucose and protein, decreased creatinine clearance and also led to marked pathological changes in the proximal tubules, as revealed by electron micrographs. An increase in phosphorylated ERK (pERK) was detected in the nuclear fraction prepared from the rat kidney cortex 24 h after CER injection. Pretreatment of rats with FTS (50 microg/kg, i.v.) attenuated the CER-induced renal dysfunction and pathological damage. FTS also suppressed CER-induced ERK activation in the kidney. In vitro treatment of the established cell line, LLC-PK1 cells, with FTS significantly ameliorated CER-induced cell injury, as measured by lactate dehydrogenase (LDH) leakage. Our results, taken together with our previous report that MEK inhibitors ameliorated CER-induced renal cell injury and ERK activation induced by CER, suggest that FTS participates in protection from CER-induced nephrotoxicity by suppressing ERK activation induced by CER.     

Modulation by cyclic AMP and phorbol myristate acetate of cephaloridine-induced injury in rat renal cortical slices

Intracellular signaling pathways of cAMP and protein kinase C (PKC) have been suggested to modulate the generation of free radicals. We investigated the effects of cAMP and phorbol myristate acetate (PMA), a PKC activator, on cephaloridine (CER)-induced renal cell injury, which has been reported to be due to the generation of free radicals. Incubation of rat renal cortical slices with CER resulted in increases in lipid peroxidation and lactate dehydrogenase (LDH) release and in decreases in gluconeogenesis and p-aminohippurate (PAH) accumulation in rat renal cortical slices, suggesting free radical-induced injury in slices exposed to CER. A derivative of cAMP ameliorated not only the increase in lipid peroxidation but also the renal cell damage induced by CER. This amelioration by a cAMP derivative of lipid peroxidation and renal cell damage caused by CER was blocked by KT 5720, a protein kinase A (PKA) inhibitor. Lipid peroxidation and the indices of cell injury were increased by PMA. PMA also enhanced CER-induced lipid peroxidation and cell damage in the slices. This enhancement by PMA of CER-induced injury was blocked by H-7, a PKC inhibitor. These results indicated that intracellular signaling pathways of cAMP and PKC modulate free radical-mediated nephrotoxicity induced by CER.     

Role of extracellular signal—regulated kinase in free radical—induced injury in kidney of rats treated with cephaloridine

We examined the role of a down stream of intracellular signaling pathway,extracellular signal-regulated kinase(ERK),in cephaloridine (CER)-induced nephrotoxicity in rats.The increase in phosphorylated ERK(pERK,activated ERK) was detected in nucleus fraction prepared from rat kidney cortex 24h after injections of antibiotic CER with the increase in BUN level.The slices prepared from rat kidney cortex were incubated in the medium containing PD980-59,a MEK1/2 inhibitor,for the measurement of free radical production and cell injure(LDH leakage).CER caused not only the increases in lipid peroxidation as an index of free radical production and LDH leakage,but also ERK activation in nucleus fraction.MEK1/2 inhibitor ameliorated CER-induced injury and suppressed ERK activation in the slices.These results suggest a possible role of MEK/ERK signaling pathway in free radical-induced CER nephrotoxicity.     

Lipid peroxidation and generations of oxygen radicals induced by cephaloridine in renal cortical microsomes of rats

To investigate whether oxygen radicals would be generated by cephaloridine (CER) in the renal cortical microsomes obtained from rats and whether the microsomal lipid peroxidation would be promoted by CER, the microsomes were incubated under a pure oxygen atmosphere in a medium containing the reduced nicotinamide adenine dinucleotide phosphate regenerating system, under various conditions. Generations of superoxide anion and hydrogen peroxide and malondialdehyde formation were all dependent on microsomal protein concentrations, incubation periods and CER concentrations. Scavengers of the microsomal lipid peroxidation induced by CER, (+)-cyanidanol-3, mannitol, sodium benzoate and N-acetyl tryptophan, which are scavengers of hydroxyl free radicals, inhibited the CER-stimulated lipid peroxidation in the microsomes. Histidine, a scavenger of hydroxyl free radicals and singlet oxygen, and alpha-tocopherol, reduced-glutathione and NN'-diphenyl-p-phenylenediamine, the three of which are non-specific antioxidants, also inhibited the CER-stimulated lipid peroxidation in the microsomes. Accordingly, our findings may strongly support that CER generates not only superoxide anions and hydrogen peroxide but also hydroxyl free radicals in the kidney, and these generated oxygen radicals react with the membrane lipids to induce peroxidation and nephrotoxicity.     

Spirulina attenuates cyclosporine-induced nephrotoxicity in rats

Cyclosporine (CsA) causes a dose-related decrease in renal function in experimental animals and humans. The generation of reactive oxygen species (ROS) has been implicated in CsA-induced nephrotoxicity. It was previously shown that Spirulina, a blue-green algae, with antioxidant properties effectively attenuated the doxorubicin-induced cardiotoxicity in mice and cisplatin-induced nephrotoxicity in rat. The present study investigated the nephroprotective role of Spirulina against CsA-induced nephrotoxicity in rats. Spirulina (500 mg kg(-1) b.w.) was administered orally for 3 days before and 14 days concurrently with CsA (50 mg kg-1 b.w.). Rats treated with CsA showed nephrotoxicity as evidenced from a significant elevation in plasma urea, creatinine, urinary N-acetyl-beta-D-glucosaminidase (beta-NAG) and a decrease in creatinine and lithium clearance. Pretreatment with Spirulina protected the rats from CsA-induced nephrotoxicity. The CsA-induced rise in plasma urea and creatinine and the decrease in creatinine and lithium clearance were attenuated by Spirulina. There was a significant increase in plasma and kidney tissue MDA with CsA. Spirulina prevented the rise in plasma and kidney tissue MDA. Histopathology of the kidney from CsA-treated rats showed severe isometric vacuolization and widening of the interstitium. However, pretreatment with Spirulina prevented such changes, and the kidney morphology was comparable to that of the control. Spirulina treatment did not alter the blood CsA levels. These results suggest that Spirulina has a protective effect against nephrotoxicity induced by CsA. This study further supports the crucial role of the antioxidant nature of Spirulina in protecting against CsA-induced oxidative stress.     

Enhancement of renal organic base accumulated by potassium dichromate.

N-Methylnicotinamide (NMN) accumulation by renal cortical slices from potassium dichromate-treated rats was not different from control at 30 min of incubation, but was substantially higher when the incubation was continued for 60 min or longer. Intravenous injection of NMN resulted in significantly higher cortex/serum concentration ratios when rats were treated 24 hr earlier with potassium dichromate. Incubation of renal cortical slices under N₂ or at O°C reduced NMN slice-medium ratios to about 1; reincubation under normal conditions returned the slice/medium ratios to normal values in controls but not in dichromate-treated animals. Replacement of drinking water with saline for 5 wk reduced both the dichromate-induced nephrotoxicity and the enhanced uptake of NMN by kidney slices. Concomitant treatment with dimercaprol and dichromate did not reduce dichromate-induced toxicity or enhancement of NMN slice accumulation. Chromium chloride elicited neither nephrotoxicity nor stimulation of NMN uptake. The enhancement of renal NMN accumulation or retention by potassium dichromate appears to be associated with the nephrotoxicity produced by this compound.     

Inhibition of active oxygen generation in guinea-pig neutrophils by biscoclaurine alkaloids

Effect of biscoclaurine alkaloids, such as cepharanthine, on active oxygen production of neutrophils was investigated. Cepharanthine inhibited both superoxide generation and luminol-dependent chemiluminescence (CL) induced by either formylmethionyl-leucyl-phenylalanine, opsonized zymosan, arachidonic acid or by phorbol myristate acetate. Ca2(+)- and phospholipid-dependent protein kinase (PKC) activity and the phosphorylation of cytoplasmic protein including 47 kDa proteins of neutrophils were also inhibited by cepharanthine; dose dependent inhibition of CL was quite similar to that of PKC. Among various biscoclaurines tested, the inhibitory effect of cepharanthine, tetrandrine and isotetrandrine was strong, but that of berbamine and cycreanine was weak; the inhibitory action of the former on lipid peroxidation and platelet aggregation were also stronger than those of the latter. These and other observations indicated that these alkaloids inhibited the active oxygen generation by way of stabilizing plasma membrane and inhibiting PKC and NADPH oxidase activation.     

姜黄素对实验性糖尿病大鼠肾脏蛋白激酶C移位活化的抑制作用

目的探讨姜黄素对实验性糖尿病大鼠肾脏蛋白激酶C（PKC）由细胞浆到细胞膜移位活化的抑制作用。方法 36只大鼠随机分为正常对照组（A组）、糖尿病组（B组）及姜黄素治疗组（C组）,每组12只。采用腹腔单剂量注射链脲佐菌素（STZ）65mg/kg建立糖尿病大鼠模型。C组给予姜黄素30mg·kg-1·d-1腹腔注射。实验第3周、第6周3组分别宰杀6只大鼠,并检测24h尿白蛋白排泄率（UAER）、肌酐清除率（Ccr）及肾重/体重;采用酶联免疫吸附法（ELISA）测定PKC活性。结果 B组UAER、Ccr、肾重/体重及肾脏细胞膜PKC活性均明显升高（P〈0.05或〈0.01）,C组大鼠上述指标均明显下降（P〈0.05或〈0.01）。结论姜黄素通过抑制糖尿病大鼠肾脏细胞PKC移位活化而对糖尿病大鼠早期肾脏病变有保护作用。     

Effect of cisplatin on calcium uptake by rat kidney cortical mitochondria

The effect of the nephrotoxic antineoplastic drug, cisplatin, on mitochondrial calcium uptake was examined in rat kidney cortical mitochondria. We treated rats with cisplatin (5 mg/kg, i.p.), and prepared and incubated the mitochondria. Uptake of calcium decreased after 24 h. The mitochondria contained platinum even 3 days after injection. Cisplatin (0.5 mM) added to incubation medium inhibited calcium uptake. Platinum accumulated in the mitochondria during incubation. Mitochondria accumulated less of another divalent cation, magnesium, in rats given cisplatin and in incubation medium with cisplatin added. The results suggest that cisplatin taken up into kidney cortical mitochondria inhibited divalent cation uptake there, which may contribute to cisplatin nephrotoxicity.     

Artocarpol A stimulation of superoxide anion generation in neutrophils involved the activation of PLC, PKC and p38 mitogen-activated PK signaling pathways

1 Artocarpol A (ART), a natural phenolic compound isolated from Artocarpus rigida, stimulated a slow onset and long-lasting superoxide anion generation in rat neutrophils, whereas only slightly activated the NADPH oxidase in a cell-free system. 2 Pretreatment of neutrophils with pertussis toxin (1 microg ml(-1)), 50 microM 2'-amino-3'-methoxyflavone (PD 98059), or 1 microM 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene (U0126) had no effect on ART-stimulated superoxide anion generation. ART (30 microM) did not induce extracellular signal-regulated kinase (ERK) phosphorylation. 3 4-(4-Fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole (SB 203580) markedly attenuated the ART-stimulated superoxide anion generation (IC50 value of 4.3+/-0.3 microM). Moreover, ART induced p38 mitogen-activated PK (MAPK) phosphorylation and activation. 4 The superoxide anion generation in response to ART was also substantially inhibited in a Ca2+-free medium, and by pretreatment with 1 microM 1-[6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-1H-pyrrole-2,5-dione (U-73122) and 100 microM 2-aminoethyldiphenyl borate (2-APB). ART (30 microM) stimulated the [Ca2+]i elevation in the presence or absence of external Ca2+, and also increased the D-myo-inositol 1,4,5-trisphosphate formation. 5 2-[1-(3-Dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)-maleimide (GF 109203X) greatly inhibited the ART-stimulated superoxide anion generation (IC50 value of 7.8+/-1.0 nM). ART increased the recruitment of PKC-alpha, -betaI, and -betaII to the plasma membrane of neutrophils, and stimulated Ca2+-dependent PKC activation in the cytosol preparation. 6 ART induced the phosphorylation of p47phox, which was attenuated by GF 109203X. Moreover, ART evoked the membrane association of p47(phox), which was inhibited by GF 109203X and SB 203580. 7 These results indicate that the ART stimulation of superoxide anion generation involved the activation of p38 MAPK, PLC/Ca2+, and PKC signaling pathways in rat neutrophils.     

Comparative study of activities in reactive oxygen species production/defense system in mitochondria of rat brain and liver,and their susceptibility to methylmercury toxicity

The involvement of oxidative stress has been suggested as a mechanism for neurotoxicity caused by methylmercury (MeHg), but the mechanism for MeHg selective toxicity in the central nervous system is still unclear. In this research, to clarify the mechanism of selective neurotoxicity caused by MeHg, the oxygen consumption levels, the reactive oxygen species (ROS) production rates and several antioxidant levels in mitochondria were compared among the cerebrum, cerebellum and liver of male Wistar rats. In addition, the alterations of these indexes were examined in MeHg-intoxicated rats (oral administration of 10 mg/kg day, for 5 days). Although the cerebrum and cerebellum in intact rats showed higher mitochondrial oxygen consumption levels and ROS production rates than the liver, glutathione peroxidase (GPX) and superoxide dismutase (SOD) activities were much lower in the cerebrum and cerebellum than in the liver. Especially, the cerebellum showed the highest oxygen consumption and ROS production rate and the lowest mitochondrial glutathione (GSH) levels among the tissues examined. In the MeHg-treated rats, decrease in the oxygen consumption and increase in the ROS generation were found only in the cerebellum mitochondria, despite a lower Hg accumulation in the mitochondrial fraction compared to the liver. Since MeHg treatment produced an enhancement of ROS generation in cerebellum mitochondria supplemented with succinate substrates, MeHg-induced oxidative stress might affect the complex II–III mediated pathway in the electron transfer chain in the cerebellum mitochondria. Our study suggested that inborn factors, high production system activity and low defense system activity of ROS in the brain, would relate to the high susceptibility of the central nervous system to MeHg toxicity.     

Ontogenic aspects of cisplatin-induced nephrotoxicity in rats

A multi-age rat model was evaluated to identify a potential age-related difference in kidney injury following administration of cisplatin (CP). Different age groups of Wistar rats (aged 3, 7, 11 and 24 weeks) were given CP intraperitoneally (6 mg/kg) and sacrificed 6 days thereafter. CP-induced nephrotoxicity caused significant decreases in body weight, creatinine clearance, urine osmolality, plasma total anti-oxidant status, cortical glutathione (GSH) concentration and superoxide dismutase activity.It increased kidney weight and plasma concentrations of creatinine and urea. It increased urinary N-acetyl-β-d-glucosaminidase activity and protein concentration. Most of the above actions were more marked as the animals advanced in age, except for the changes in GSH, which were similar in all age groups.     

Effects of misoprostol on cisplatin-induced renal damage in rats

Cisplatin (CP) is a potent anticancer drug. However, it has side effects on kidney such as nephrotoxicity. Abnormal production of reactive oxygen species (ROS) has been accused in the etiology of CP-induced nephrotoxicity. Several ROS scavengers have been reported to prevent nephrotoxicity after CP administration. In this study, we used prostaglandin E1 (PGE1) analogues misoprostol (MP) to reduce this damage. MP has gained considerable interest as a ROS scavenger. Rats were received a single injection of CP (5 mg/kg, i.p.) with or without MP pretreatment (200 mcg/kg, orally). The renal tissue morphology was investigated by light microscopy. Trunk blood was also obtained to determine lipid peroxidation product malondialdehyde (MDA) and activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT). CP administration increased MDA production and decreased SOD and CAT levels in the kidney tissue when compared to the control group. Morphological damage in CP administrated rats was also severe in the kidney tissue. MP treatment after CP application protected the renal tissues from CP’s side effect. These findings indicate that MP has beneficial effects on CP induced nephrotoxicity in rats.     

Nephrotoxicity of hexachloro-1:3-butadiene in the rat: The effect of age,sex, and strain

Adult male rats are less susceptible to hexachloro-1:3-butadiene-induced nephrotoxicity than adult female and young male rats. A single dose of 50 mg/kg hexachloro-1:3-butadiene (HCBD) ip in adult Alderley Park (Wistar-derived) females produced marked renal tubular necrosis and an increased plasma urea by 24 hr. Young male rats were also more susceptible to HCBD-induced nephrotoxicity; a dose of 25 mg/kg produced marked tubular necrosis and an increased plasma urea in 21-day-old rats, while a dose of 200 mg/kg was required to produce a similar response in adult males. p-Aminohippurate accumulation by thin slices of renal cortex from rats treated 24 hr previously with HCBD was reduced in adult but not in young male rats. HCBD was more toxic to young male rats (21 and 29 days old, LD50 57 and 96 mg/kg. respectively) than to adult males (7 weeks old, LD50 360 mg/kg). HCBD administration produced a more marked nephrotoxicity in 21-day-old rats treated with phenobarbital in their drinking water for 7 days than in rats of the same age not treated with phenobarbital. Associated with the increased susceptibility of female rats, renal nonprotein sulfhydryl content (NP-SH) was decreased in female but not in male rats 4 hr after HCBD administration. This decrease suggests conjugation of HCBD by the female rat kidney. The sex and age differences observed in nephrotoxicity due to HCBD are probably related to differences in hepatic and renal enzymes responsible for the detoxification and/or activation of HCBD. Fischer 344 rats were slightly more susceptible and Long Evans rats slightly less susceptible than the Alderley Park strain to HCBD-induced nephrotoxicity, although the differences were not as marked as those seen with age and sex.     

Topiramate and vitamin e modulate antioxidant enzyme activities, nitric oxide and lipid peroxidation levels in pentylenetetrazol-induced nephrotoxicity in rats

Previous studies have shown that generation of free radicals is increased following pentylenetetrazol kindling, due to increased cytosolic Ca2+ concentrations. Topiramate, a voltage-gated calcium channel inhibitor, has an evident effect in the treatment of childhood epilepsy; however, topiramate may cause nephrotoxicity. We investigated the effects of topiramate and vitamin E administration on pentylenetetrazol-induced nephrotoxicity in rats by evaluation of lipid peroxidation, nitric oxide, glutathione peroxidase, catalase and superoxide dismutase values. Forty male Wistar rats were randomly divided into five equal groups. Group 1 was used as control and group II received a single dose of pentylenetetrazol. Fifty and 100 mg/kg topiramate daily were intragastrically administered to rats in groups III and IV for 7 days, respectively. Intragastric 100 mg topiramate (daily for 7 days) and intraperitoneal vitamin E (150 mg/kg, daily for 3 days) combination were given to animals in group V before a single-dose pentylenetetrazol administration. Serum and kidney samples were taken after 3 hr of pentylenetetrazol administration. Pentylenetetrazol resulted in a significant increase in nitric oxide levels of serum and kidney, and lipid peroxidation levels of kidney although superoxide dismutase and catalase activities in the kidney was reduced by pentylenetetrazol administration. The lipid peroxidation levels in serum and kidneys and the nitric oxide levels in kidneys of groups III, IV and V were decreased by topiramate although the superoxide dismutase and catalase activities in the kidneys were increased. Lipid peroxidation and nitric oxide levels were reduced by the topiramate and vitamin E combination compared to only topiramate. Glutathione peroxidase activity was not affect by pentylenetetrazol, topiramate and vitamin E administrations. In conclusion, topiramate and vitamin E have protective effects on pentylenetetrazol-induced nephrotoxicity by inhibition of free radicals and by support of the antioxidant redox system.     

Effect of dimethyl sulfoxide on gentamicin-induced nephrotoxicity in rats

Nephrotoxicity of gentamicin (GM) has been suggested to be mediated by the generation of reduced oxygen metabolites. The present study investigated the possible protective role of the free radical scavenger dimethyl sulfoxide (DMSO) on some indices of GM nephrotoxicity in rats. The antibiotic was injected intramuscularly (i.m.) at a dose of 100 mg/kg for six consecutive days, either with or without treatment with DMSO (12.5%, 25% or 50% in saline) at an intraperitoneal (i.p.) dose of 2 ml/kg 4 days before GM, and concomitantly with GM treatment thereafter. DMSO (25% in saline) was also given as above to rats treated with GM at i.m. doses of 25, 50 or 100 mg/kg for six consecutive days. GM caused dose-dependent significant increases in the concentrations of urea and creatinine in plasma, and in thiobarbituric acid reactive substances (TBARS) level in the kidney cortex and also caused significant decreases in the concentrations of reduced glutathione (GSH) and superoxide dismutase (SOD) activity. In GM-treated rats, DMSO dose-dependently lowered the elevated plasma urea and creatinine concentrations, and the rise in cortical TBARS. It also restored the levels of GSH and SOD activity to near normal. DMSO (25%) was effective in completely preventing the development of signs of nephrotoxicity of G (50 mg/kg). Treatment of the rats with DMSO alone, at any of the above doses, did not alter significantly any of the renal or hepatic function tests studied, and did not appear to adversely affect the kidney or liver histology. However, the efficacy and safety of DMSO require further studies. It is suggested that DMSO has potential protective effect against GM nephrotoxicity in rats.     

Inhibition of phosphate transport in rat heart mitochondria by 3'-azido-3'-deoxythymidine due to stimulation of superoxide anion mitochondrial production

In order to gain some insight into the mechanism by which 3'-azido-3'-deoxythymidine (AZT) damages mitochondria, we investigated whether externally added AZT can stimulate reactive oxygen species (ROS) production by rat heart mitochondria (RHM). An increase in superoxide anion ((O(2)(.-)) production was measured in RHM added with AZT, by using a photometrically method which allows an early O(2)(.-) detection by following the absorbance increase at 550 nm due to the ferricytochrome c reduction. Such an increase was found to be prevented from externally added superoxide dismutase. The stimulation of O(2)(.-) mitochondrial production induced by AZT was found to occur under conditions in which mitochondrial oxygen consumption was prevented by both inhibitors of electron flow and ATP synthesis. Since ROS can cause mitochondrial carrier impairment, we investigated whether AZT can affect mitochondrial permeability in virtue of its capability to stimulate ROS production. In this regard, we studied the transport of phosphate (P(i)), by measuring the mitochondrial shrinkage that takes place as a result of P(i) uptake by RHM previously swollen in a calcium acetate medium. As a result of the AZT-dependent O(2)(.-) production, uncompetitive inhibition of the rate of P(i) transport in RHM was found (K(i) of about 10 microM), consistently, such an inhibition was found to prevent by certain known ROS scavengers, i.e. superoxide dismutase, the antioxidant Vitamin C and reduced gluthatione.