Excretion of malondialdehyde, formaldehyde, acetaldehyde, acetone and methyl ethyl ketone in the urine of rats given an acute dose of malondialdehyde

Dosing-time dependent oxidative effects of sodium nitroprusside in brain, kidney, and liver of mice

The purpose of this study was to investigate if the oxidative effects of sodium nitroprusside (SNP) are dosing-time dependent. Therefore, the variation of malondialdehyde (MDA) status was assessed after a single i.p. administration of SNP (2.5mgkg(-1) b.w.) or vehicle (9‰ NaCl) to different and comparable groups of mice (n=48) at two different circadian times (1 and 13h after light onset [HALO]). Brain, kidney, and liver tissues were excised over 36h, and their MDA contents were estimated at 0, 1, 3, 6, 9, 12, 24, and 36h after SNP administration.

RESULTS

indicated mean MDA level was not significantly changed in each investigated tissue compared with the control. In contrast, the mean MDA value varied among organs and was comparable in brain and liver but lower than in kidney. The data show SNP significantly (P<0.05) increases MDA status in both tissues and exerts time-dependent oxidative effects with the greatest toxicity coinciding with the beginning of the diurnal rest span (local time: 08:00h, i.e., at 1 HALO). The obtained results reveal SNP-induced oxidative damage (evidenced by MDA accumulation) varies according to both the dosing-time and the target organ.

An optimized method for the measurement of acetaldehyde by high-performance liquid chromatography

BACKGROUND

Acetaldehyde is produced during ethanol metabolism predominantly in the liver by alcohol dehydrogenase and rapidly eliminated by oxidation to acetate via aldehyde dehydrogenase. Assessment of circulating acetaldehyde levels in biological matrices is performed by headspace gas chromatography and reverse phase high-performance liquid chromatography (RP-HPLC).

METHODS

We have developed an optimized method for the measurement of acetaldehyde by RP-HPLC in hepatoma cell culture medium, blood, and plasma. After sample deproteinization, acetaldehyde was derivatized with 2,4-dinitrophenylhydrazine (DNPH). The reaction was optimized for pH, amount of derivatization reagent, time, and temperature. Extraction methods of the acetaldehyde-hydrazone (AcH-DNP) stable derivative and product stability studies were carried out. Acetaldehyde was identified by its retention time in comparison with AcH-DNP standard, using a new chromatography gradient program, and quantitated based on external reference standards and standard addition calibration curves in the presence and absence of ethanol.

RESULTS

Derivatization of acetaldehyde was performed at pH 4.0 with an 80-fold molar excess of DNPH. The reaction was completed in 40 minutes at ambient temperature, and the product was stable for 2 days. A clear separation of AcH-DNP from DNPH was obtained with a new 11-minute chromatography program. Acetaldehyde detection was linear up to 80 μM. The recovery of acetaldehyde was >88% in culture media and >78% in plasma. We quantitatively determined the ethanol-derived acetaldehyde in hepatoma cells, rat blood and plasma with a detection limit around 3 μM. The accuracy of the method was <9% for intraday and <15% for interday measurements, in small volume (70 μl) plasma sampling.

CONCLUSIONS

An optimized method for the quantitative determination of acetaldehyde in biological systems was developed using derivatization with DNPH, followed by a short RP-HPLC separation of AcH-DNP. The method has an extended linear range, is reproducible and applicable to small-volume sampling of culture media and biological fluids.

Malondialdehyde Content and Circadian Variations in Brain, Kidney, Liver, and Plasma of Mice

In aerobic organisms, the use of oxygen (O(2)) to produce energy is associated with the production of Reactive Oxygen Species (ROS), which reacts with biological molecules to produce oxidized metabolites such as malondialdehyde (MDA). This experiment focused on male Swiss mice 12 weeks of age synchronized for 3 weeks by the 12 h light (rest)/12 h dark (activity) span. Different and comparable groups of animals (n=10) were sacrificed at six different circadian stages: 1, 5, 9, 13, 17, and 21 h after light onset (HALO). The 24 h mean MDA level varied among organs of mice in non-stress conditions and was comparable in brain and liver but lower than in kidney. As the MDA 24 h status constitutes only a part of ROS damages in sites differing by their oxygen use, lipid composition, and detoxification capacity, the temporal patterns of their MDA content were comparatively studied in relationship to the animal rest-activity cycle. The results revealed significant circadian rhythms with the peak time located during the rest span (approximately =5 HALO) for both brain and liver, but during the activity span for the kidney ( approximately =21 HALO) and plasma (approximately =13 HALO). This chronobiological study showed that under physiological conditions, lipid peroxidation depends on several factors. The MDA peak/trough might be used as a tool to detect moments of high/low sensitivity of tissues to ROS attack in rodents.

Does glucose present in the dialysate limit oxidative stress in patients undergoing regular hemodialysis?

BACKGROUND

Decreased glucose concentration in the blood causes the inhibition of the hexose monophosphate (HMP) cycle in the erythrocyte. NADPH, which is the source of the reductive equivalents necessary for the reproduction of glutathione (GSH), is not regenerated. The presence of glucose in dialysate should provide the stability of its concentration in the blood of patients undergoing hemodialysis (HD). The aim of the study was to assess the influence of glucose in the dialysate on the intensity of oxidative stress in patients undergoing regular HD.

METHODS

The study comprised 43 patients hemodialyzed with dialysate containing (HD-g(+)) or not containing glucose (HD-g(-)). The concentrations of the products of reaction with thiobarbituric acid-reactive substance (TBARS) and GSH as well as the activity of erythrocyte superoxide dismutase were determined. Glucose concentrations in the blood before and immediately after dialysis were also measured.

RESULTS

After flow-through dialysis the glucose concentration in the blood decreases both when dialysate does not contain glucose (4.8 vs. 1.6 mmol/l) and when dialysate contains glucose (6.6 vs. 5.8 mmol/l). HD caused changes in the TBARS concentration: in the HD-g(+) group the concentration decreased after HD, whereas in the HD-g(-) group it increased. In both groups of patients studied the GSH concentration changed after HD; in the HD-g(-) group it decreased and in the HD-g(+) group it increased. The results obtained in the groups of patients examined were confirmed by in vitro studies.

CONCLUSIONS

The presence of glucose in the dialysate guarantees the normal activity of the HMP cycle, which provides the production of reductive equivalents for the regeneration of reduced GSH - free radicals scavenger - and therefore the limitation of oxidative stress.

Plasma Malondialdehyde Increases Transiently after Ischemic Forearm Exercise

Exercise and ischemia-reperfusion (I-R) have previously been shown to induce oxidative stress in skeletal muscle. Previous studies have demonstrated conflicting results when exercise-induced oxidative stress has been measured using plasma carbonyls, specifically malondialdehyde (MDA). These conflicting results likely stem from the timing and method utilized to measure plasma carbonyls.

PURPOSE

To determine the concentration and timing of aldehyde and ketone generation after ischemic forearm exercise utilizing HPLC analysis.

METHODS

Plasma carbonyls, including MDA, 17-beta-estradiol, and lactate, were measured after a forearm ischemic exercise test (FIT) in males and females (in both phases of their menstrual cycle). Blood flow was occluded to the forearm, and six cycles of maximal isometric handgrip exercise were executed using a 9:1, duty:rest cycle, for 60 s. Blood samples were collected pre, immediately post, and 1, 3, and 10 min post-FIT.

RESULTS

Plasma MDA increased similarly for both males and females immediately post and 1 min post-FIT (P<0.05) and returned to baseline levels by 3 min post-FIT. Ischemic exercise did not alter plasma concentrations of other measured carbonyls, and gender and menstrual cycle did not influence any measured variable (P>0.05), except for lactate concentrations, which increased more for males (P<0.05). Force was higher for males at all time points (P<0.05); however, there was no effect of gender on percent fatigue.

CONCLUSIONS

Future studies must consider sampling times after metabolic stress in order to quantify changes in MDA concentration.

Erythrocyte glutathione peroxidase activity, plasma malondialdehyde and erythrocyte glutathione levels in hemodialysis and CAPD patients

OBJECTIVES

Cardiovascular disease is the major cause of mortality in patients receiving hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) due to chronic renal failure. Increased lipid peroxidation and depletion of antioxidants may contribute to increased risk of atherosclerosis. We have therefore assessed the effect of hemodialysis and CAPD on oxidant and antioxidant status.

DESIGN AND METHODS

Plasma malondialdehyde (MDA), Glutathione (GSH) levels and glutathione peroxidase (Gpx) activities were determined in 20 healthy persons (control), 20 patients on HD, 16 patients on CAPD.

RESULTS

MDA was elevated in posthemodialysis and CAPD patients in comparison to prehemodialysis and control groups (posthemodialysis 1.39 +/- 0.38 nmol/mL, CAPD 1.26 +/- 0.27 nmol/mL, prehemodilaysis 0.83 +/- 0.22 nmol/mL, controls 0.72 +/- 0.21 nmol/mL p < 0.0001). With respect to antioxidants, glutathione levels were significantly lower in prehemodialysis, posthemodialysis and CAPD groups than those in control group (prehemodialysis 16.82 +/- 6.73 mg/dL RBC, posthemodialysis 31.43 +/- 11.88 mg/dL RBC, CAPD 40 +/- 12.72 mg/dL RBC, controls 62.26 +/- 24.01 mg/dL RBC, p < 0.0001). While erythrocyte GSH levels were significantly lower in the prehemodialysis patients than those in posthemodialysis and CAPD patients (p < 0.0001), it was significantly lower in posthemodialysis patients than those in CAPD patients (p < 0.05). There were no significant differences with respect to erythrocyte Gpx levels among the groups (p > 0.05).

CONCLUSIONS

These findings indicate oxidative stress in patients with chronic renal failure which is further exacerbated by hemodialysis and CAPD, as evidenced by increased lipid peroxidation and low antioxidant levels.

Toxicity of oxidized fats II: tissue levels of lipid peroxides in rats fed a thermally oxidized corn oil diet

Male Wistar albino rats were fed for 21 days on a diet in which fat (12%) was included either as fresh corn oil, malonaldehyde content = 0.11+/-0.05 micro microg/g (control) or thermally oxidized corn oil, malonaldehyde content = 0.20+/-0.03 microg/g (experimental) and the tissue levels of lipid peroxides in six organs-namely, liver, kidney, brain, heart, lungs and testes-were determined. Of the organs studied, significantly (P < 0.1) higher concentrations of lipid peroxides were observed only in the liver and kidney of the experimental rats. In the course of the feeding, the experimental rats showed significantly (P < 0.1) lower gains in body weights as well as higher relative liver weights than the control rats.

Deamination of methylamine and aminoacetone increases aldehydes and oxidative stress in rats

Semicarbazide-sensitive amine oxidase (SSAO)-mediated deamination of methylamine and aminoacetone in vitro produces carbonyl compounds, such as formaldehyde and methylglyoxal, which have been proposed to be cytotoxic and may be responsible for some pathological conditions. An HPLC procedure was developed to assess different aldehydes, which were derivatized with 2,4-dinitrophenylhydrazine (DNPH). We have demonstrated in vivo deamination of methylamine and aminoacetone by examining the excretion of formaldehyde and methylglyoxal, respectively, in rats. Following chronic administration of methylamine, the urinary level of malondialdehyde (MDA), an end product of lipid peroxidation, was also found to be substantially increased. A selective SSAO inhibitor blocked the increase of MDA. The results support the idea that increased SSAO-mediated deamination of methylamine and aminoacetone can be a potential cytotoxic risk factor.

Comparison of urinary and plasma malondialdehyde in preterm infants

The measurement of malondialdehyde (MDA) in biological fluids remains a popular method for the quantification of free radical damage to lipids in vivo. Several diseases of prematurity are thought to be related to oxidative injury and previous studies have found elevated MDA in plasma and urine in preterm infants. Our aim was to investigate the relationship between plasma and urinary MDA levels in preterm infants during the first week of life using a high-performance liquid chromatography (HPLC) based, thiobarbituric acid (TBA) assay with paired plasma and urine samples. We obtained 50 paired samples, and were unable to demonstrate a relationship between the two parameters after the first day of life. In 18 cases a further urine sample was collected 24 h later. There was a positive correlation (r = 0.54, P = 0.02) between plasma MDA and urinary MDA 24 h later. The finding that plasma changes in MDA are reflected in urine 24 h later validates the use of urinary MDA as a marker of whole body lipid peroxidation in populations without renal disease.

Influence of dialysis on plasma lipid peroxidation products and antioxidant levels

In patients with end-stage renal failure (ESRF), the incidence of atherosclerosis and cancer is increased. The importance of lipid peroxidation (LPO) products in the pathogenesis of these complications has recently been emphasized. The LPO products malondialdehyde (MDA) and hexanal, lipophilic antioxidants and erythrocyte glutathione (GSH) were estimated in 10 pediatric hemodialysis (HD) patients before and after HD and in 11 peritoneal dialysis (CPD) patients. Before HD, MDA was elevated [median (interquartile range): 384.5 (110 to 501) nM; normal < 150 nM], whereas plasma hexanal levels were normal in all patients [130.5 (88 to 222) nM; < 320 nM]. HD decreased MDA concentrations on average by 88% but did not change hexanal levels. CPD patients exhibited high plasma MDA concentrations [371 (287 to 468) nM], whereas hexanal was in the low normal range [56 (51 to 81) nM]. Antioxidants were normal in both groups and unchanged during HD. GSH decreased slightly during HD. We hypothesize that MDA may accumulate in ESRF due to reduced plasma clearance. Our results argue against a general increase of LPO in uremia.

Cadmium-induced excretion of urinary lipid metabolites, DNA damage, glutathione depletion, and hepatic lipid peroxidation in Sprague-Dawley rats

Recent studies have described lipid peroxidation to be an early and sensitive consequence of cadmium exposure, and free radical scavengers and antioxidants have been reported to attenuate cadmium-induced toxicity. These observations suggest that cadmium produces reactive oxygen species that may mediate many of the untoward effects of cadmium. Therefore, the effects of cadmium (II) chloride on reactive oxygen species production were examined following a single oral exposure (0.50 LD50) by assessing hepatic mitochondrial and microsomal lipid peroxidation, glutathione content in the liver, excretion of urinary lipid metabolites, and the incidence of hepatic nuclear DNA damage. Increases in lipid peroxidation of 4.0- and 4.2-fold occurred in hepatic mitochondria and microsomes, respectively, 48 h after the oral administration of 44 mg cadmium (II) chloride/kg, while a 65% decrease in glutathione content was observed in the liver. The urinary excretion of malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT), and acetone (ACON) were determined at 0-96 h after Cd administration. Between 48 and 72 h posttreatment maximal excretion of the four urinary lipid metabolites was observed with increases of 2.2- to 3.6-fold in cadmium (II) chloride-treated rats. Increases in DNA single-strand breaks of 1.7-fold were observed 48 h after administration of cadmium. These results support the hypothesis that cadmium induces production of reactive oxygen species, which may contribute to the tissue-damaging effects of this metal ion.