F2-isoprostane induced prostaglandin formation in the rabbit

F(2)-isoprostanes, non-enzymatic free radical mediated products of arachidonic acid, have shown to form during various oxidant stress status and have potent biological effects. This study investigates to what extent 8-iso-PGF(2alpha) (a major F(2)-isoprostane), a bioactive product of lipid peroxidation can modify endogenous prostaglandin F(2alpha) (PGF(2alpha)) formation since prostaglandins are inflammatory as well as potent vasoregulatory substances that modulate diverse important physiological functions, and also form during acute and chronic inflammation. An immediate appearance and disappearance of 8-iso-PGF(2alpha) was seen in both plasma and urine within a short interval after i.v. administration of 43 microg/kg of 8-iso-PGF(2alpha) to the rabbits. A successive but differential formation of PGF(2alpha) resulted in a rapid and pulsatile increase of plasma 15-keto-dihydro-PGF(2alpha), a major metabolite of primary PGF(2alpha). Later, this compound was excreted efficiently as intact compound into the urine during the 3 h of experiment. A 8-fold increase of PGF(2alpha) metabolite in plasma at 10 min and 12-fold increase in the urine at 30-60 after the i.v. administration of 8-iso-PGF(2alpha) was observed which continued throughout the 3 h of experiment. This observation suggests that pharmacologically administered or endogenously produced 8-iso-PGF(2alpha) during oxidant stress induces prostaglandin formation presumably through the classical cyclooxygenase-catalysed arachidonic acid oxidation which might be inflammatory itself to the cells and exerts further vasoconstrictive effects.     

Bioavailable flavonoids to suppress the formation of 8-OHdG in HepG2 cells

Antioxidative flavonoids, ubiquitously included in vegetables, fruits and teas, are expected to prevent degenerative diseases. It is unclear, however, whether flavonoids can enter the cellular nuclei and suppress the oxidative damage of DNA. Here, several flavonoids at the physiological concentration of 10 microM were dosed to 2.5x10(7) HepG2 cells. The nuclei were isolated and determined in the incorporated flavonoid levels, and simultaneously exposed to reactive oxygen generated from 25 mM of 2,2'-azobis(2-amidinopropane) dihydrochloride. Most of the tested flavonoids were incorporated into the cells in the range between 1000 and 1600 pmol/10(7) cells, and were in the nuclei at 250-450 pmol/10(7) cells at the maximum incorporation after 30min of cell incubation. In the cells, 23% of quercetin (3,5,7,3',4'-OH) and 8% of luteolin (5,7,3',4'-OH) were the original aglycone forms and the others were the methylated and gulucuronide/sulfate conjugates, while 72% of kaempferol (3,5,7,4'-OH) and 85% of apigenin (5,7,4'-OH) were aglycones and located in the nuclei at the similar ratio of metabolites. Quercetin and luteolin significantly suppressed the formation of 8-oxo-7,8-dihydrodeoxyguanosine by 25% and 15%, respectively, compared to those in 0-time incubated cells with the flavonoids. Under such conditions of low level and hydroxyl-masked in the nuclei, the limited flavonoids were bioavailable antioxidants to prevent genetic damage and they were B-ring catechols such as quercetin and luteolin.     

Determinants of F2-isoprostane biosynthesis and inhibition in man

Several cardiovascular risk factors are characterized by the coexistence of low-grade inflammation, enhanced oxidative stress and lipid peroxidation. It has been hypothesized that F2-isoprostanes, a product of in vivo lipid peroxidation, may transduce the effects of metabolic and hemodynamic abnormalities into increased cardiovascular risk. Thus, the formation of these compounds, including urinary 8-iso-Prostaglandin (PG) F2alpha, has been investigated in clinical settings putatively associated with oxidant stress. Enhanced lipid peroxidation together with increased in vivo platelet activation have been found in association with the major cardiovascular risk factors. Thus, F2-isoprostanes may transduce the effects of oxidant stress associated with complex metabolic disorders into specialized forms of cellular activation. In particular, the low-grade inflammatory state characterizing metabolic disorders such as obesity, hypercholesterolemia, type 2 diabetes mellitus, and homozygous homocystinuria may be the primary trigger of thromboxane-dependent platelet activation mediated, at least in part, through enhanced lipid peroxidation. Moreover, oxidative stress may promote endothelial dysfunction through increased production of reactive oxygen species that inactivate nitric oxide. Accumulation and activation of leukocytes plays a key role in atherosclerosis and its complications. Interestingly, neutrophil adhesion induced by minimally modified low-density lipoproteins is mainly mediated by F2-isoprostanes. Although epidemiological studies suggest an inverse relationship between antioxidant vitamin intake and cardiovascular disease, several clinical trials have obtained conflicting results on the effects of vitamin E supplementation on the risk of cardiovascular events. On the other hand, the use of F2-isoprostane formation as a biochemical end-point for dose-finding studies of vitamin E supplementation has helped clarifying the unique features of its pharmacodynamic effects on lipid peroxidation. This information could be extremely valuable in the selection of the appropriate patient subgroups that may benefit from antioxidant interventions.     

Increased urinary F2-isoprostane excretion in alcoholic liver disease

Free radical-induced lipid peroxidation (LP) is thought to be important in alcoholic liver disease (ALD), however, direct demonstration of increased LP in patients with ALD has been difficult. Quantification of F2-isoprostanes (F2-isoP), prostanoids produced by peroxidation of arachidonic acid, in plasma and urine are sensitive and specific indices of LP in vivo. To determine if LP is increased in ALD, 24-h urinary excretion of F2-isoPs were measured in 10 patients hospitalized because of ALD. The mean urinary excretion of the F2-isoP in the ALD patients' urine was 9.6+/-3.5 ng/mg creatinine, which was significantly elevated compared to controls' urinary excretion, which was 1.7+/-0.2 ng/mg creatinine (p<.01). The urinary excretion of F2-isoP decreased to 3.6+/-1.1 ng/mg creatinine as the patients improved clinically with abstinence over the 1-month period. These data suggest that lipid peroxidation, as assessed by this noninvasive method, is increased in patients with acute ALD and decreases with time as the patients improve clinically with abstinence.     

F2-isoprostane excretion rate and diurnal variation in human urine

8-Iso-PGF2alpha is formed in vivo by non-enzymatic free radical catalysed oxidation of arachidonic acid. Urinary measurement of this compound has previously been shown to reflect the oxidative stress of the body in human and animal studies. To investigate the normal excretion rate and a possible diurnal variation of 8-iso-PGF2alpha excretion in humans urinary samples were collected from ten healthy volunteers of both sexes at different times during a day and as a 24-h urine sample. The samples were analyzed by a newly developed radioimmunoassay with a specific antibody against free 8-iso-PGF2alpha. There was no diurnal variation in the urinary levels of 8-iso-PGF2alpha during the day in this study. Neither was there any statistically significant difference between the 8-iso-PGF2alpha levels at any time of the day or in the morning urine samples compared to the 24-h urine samples. In conclusion, all urine samples collected at any time of the day, preferably a morning urine sample (representative urine from 6-8 hours), can thus be used to obtain a reliable and adequate value of the amount of the 8-iso-PGF2alpha excretion in urine in healthy individuals.     

Hemoglobin vesicles containing methemoglobin and L-tyrosine to suppress methemoglobin formation in vitro and in vivo

Hemoglobin (Hb) vesicles have been developed as cellular-type Hb-based O(2) carriers in which a purified and concentrated Hb solution is encapsulated with a phospholipid bilayer membrane. Ferrous Hb molecules within an Hb vesicle were converted to ferric metHb by reacting with reactive oxygen species such as hydrogen peroxide (H(2)O(2)) generated in the living body or during the autoxidation of oxyHb in the Hb vesicle, and this leads to the loss of O(2) binding ability. The prevention of metHb formation by H(2)O(2) in the Hb vesicle is required to prolong the in vivo O(2) carrying ability. We found that a mixed solution of metHb and L-tyrosine (L-Tyr) showed an effective H(2)O(2) elimination ability by utilizing the reverse peroxidase activity of metHb with L-Tyr as an electron donor. The time taken for the conversion of half of oxyHb to metHb (T(50)) was 420 min for the Hb vesicles containing 4 g/dL (620 microM) metHb and 8.5 mM L-Tyr ((metHb/L-Tyr) Hb vesicles), whereas the time of conversion for the conventional Hb vesicles was 25 min by stepwise injection of H(2)O(2) (310 microM) in 10 min intervals. Furthermore, in the (metHb/L-Tyr) Hb vesicles, the metHb percentage did not reach 50% even after 48 h under a pO(2) of 40 Torr at 37 degrees C, whereas T(50) of the conventional Hb vesicles was 13 h under the same conditions. Moreover, the T(50) values of the conventional Hb vesicles and the (metHb/L-Tyr) Hb vesicles were 14 and 44 h, respectively, after injection into rats (20 mL/kg), confirming the remarkable inhibitory effect of metHb formation in vivo in the (metHb/L-Tyr) Hb vesicles.     

Flavanol-rich cocoa drink lowers plasma F(2)-isoprostane concentrations in humans

Flavan-3-ols are potent antioxidants in vitro, but convincing evidence for antioxidant action in vivo is lacking. We examined whether an oxidative stress-mediated increase in plasma F(2)-isoprostanes is counteracted by a flavanol-rich cocoa beverage. Twenty volunteers were examined in a comparative randomized double-blind crossover design with respect to ingestion of high-flavanol cocoa drink (HFCD; 187 mg flavan-3-ols/100 ml) vs. low-flavanol cocoa drink (LFCD; 14 mg/100 ml). With 10 individuals, the treatment was combined with strenuous physical exercise. Total (esterified plus nonesterified) F(2)-isoprostanes were analyzed by GC/MS. LFCD caused a slight increase in the mean (+/- SEM) plasma concentrations of F(2)-isoprostanes 2 and 4 h after intake (2.16 +/- 0.19 nM at 4 h vs. 1.76 +/- 0.11 nM at 0 h, n = 10), which may be attributable to postprandial oxidative stress. This increase did not occur with HFCD (1.57 +/- 0.06 nM at 4 h vs. 1.65 +/- 0.10 nM at 0 h, n = 10). The difference in F(2)-isoprostanes 2 and 4 h after intake of HFCD vs. LFCD became statistically significant when the intake was combined with physical exercise (P < 0.01, ANOVA). We conclude that dietary flavanols, using cocoa drink as example, can lower the plasma level of F(2)-isoprostanes, indicators of in vivo lipid peroxidation.     

Dietary flavonoids suppress azoxymethane-induced colonic preneoplastic lesions in male C57BL/KsJ-db/db mice

Obesity is known to be a risk factor for colon carcinogenesis. Although there are several reports on the chemopreventive abilities of dietary flavonoids in chemically induced colon carcinogenesis, those have not been addressed in an obesity-associated carcinogenesis model. In the present study, the effects of 3 flavonoids (chrysin, quercetin and nobiletin) on modulation of the occurrence of putative preneoplastic lesions, aberrant crypt foci (ACF), and β-catenin-accumulated crypts (BCACs) in the development of colon cancer were determined in male db/db mice with obesity and diabetic phenotypes. Male db/db mice were given 3 weekly intraperitoneal injections of azoxymethane (AOM) to induce the ACF and BCAC. Each flavonoid (100 ppm), given in the diet throughout the experimental period, significantly reduced the numbers of ACF by 68–91% and BCAC by 64–71%, as well as proliferation activity in the lesions. Clinical chemistry results revealed that the serum levels of leptin and insulin in mice treated with AOM were greater than those in the untreated group. Interestingly, the most pronounced suppression of development of preneoplastic lesions and their proliferation were observed in the quercetin-fed group, in which the serum leptin level was lowered. Furthermore, quercetin-feeding decreased leptin mRNA expression and secretion in differentiated 3T3-L1 mouse adipocytes. These results suggest that the present dietary flavonoids are able to suppress the early phase of colon carcinogenesis in obese mice, partly through inhibition of proliferation activity caused by serum growth factors. Furthermore, they indicate that certain flavonoids may be useful for prevention of colon carcinogenesis in obese humans.     

Intra-day variation of in vivo prostaglandin F2alpha formation in healthy subjects

Prostaglandin F(2alpha) (PGF(2alpha)) is a major stable prostaglandin formed in vivo in physiological and pathophysiological situations and has mainly potent vasoconstrictive and pro-inflammatory properties. PGF(2alpha) is now used as an indicator of acute and chronic inflammation in human clinical settings but the extent of daily variation of PGF(2alpha)in vivo in healthy humans is unknown. We quantified levels of the PGF(2alpha) metabolite 15-keto-dihydro-PGF(2alpha) in 10 healthy males and females in spot urine samples during the day (including morning urine sample) and in 24-h urine during the same day. The intra-day coefficient of variation was 20.9%. However, the total mean value of 15-keto-dihydro-PGF(2alpha) in urine collected in the morning did not significantly differ from the mean level of 15-keto-dihydro-PGF(2alpha) in the 24-h urine samples in the 10 subjects. 15-Keto-dihydro-PGF(2alpha) levels in morning urine showed a positive linear correlation with levels of 15-keto-dihydro-PGF(2alpha) in 24-h urine (R=0.72, P<0.05). In conclusion, formation of PGF(2alpha) shows a biological variation within the day in healthy humans which should not be overlooked when planning a clinical study. Single morning urine samples can be used as an alternative to 24-h urine collections for quantification of PGF(2alpha) formation to simplify the sampling regime in larger clinical studies.     

F(2)-isoprostane and prostaglandin F(2 alpha)metabolite excretion rate and day to day variation in healthy humans.

Isoprostanes are mainly formed in vivo by a non-enzymatic free radical catalysed oxidation of arachidonic acid. Studies have indicated that a major isoprostane, 8-iso-PGF(2 alpha)in plasma and urine is a reliable biomarker of oxidative stress. Prostaglandins are formed by enzymatic oxidation of arachidonic acid catalysed by cyclooxygenase (COX). 15-Keto-dihydro-PGF(2 alpha), a major metabolite of prostaglandin F(2 alpha)in plasma, and also found in urine, is considered to be a useful biomarker of inflammation. To investigate the excretion pattern and day to day variation of 8-iso-PGF(2 alpha)and 15-keto-dihydro-PGF(2 alpha)in healthy individuals, morning urine samples were collected from 13 volunteers on 10 successive days. The samples were analysed for free 8-iso-PGF(2 alpha)and 15-keto-dihydro-PGF(2 alpha)by radioimmunoassay. The mean excretion rate of 8-iso-PGF(2 alpha)was 0.27+/-0.11 nmol/mmol creatinine (mean+/-SD, n=13) and the coefficient of variation was 42% during the 10 days. The mean excretion rate of 15-keto-dihydro-PGF(2 alpha)was 0.46+/-0.19 nmol/mmol creatinine, giving a coefficient of variation of 41%. The mean values of 8-iso-PGF(2 alpha)were significantly correlated with the mean values of 15-keto-dihydro-PGF(2 alpha)(r=0.68, P=0.01). In conclusion, day to day biological variation in urinary excretion rate of 8-iso-PGF(2 alpha)and 15-keto-dihydro-PGF(2 alpha)should be taken into account in evaluating a clinical study unless a large increase or decrease of these parameters has been obtained.     

F2-isoprostane, inflammation, cardiac function and oxygenation in the endotoxaemic pig

Prostaglandins are profoundly involved in endotoxaemic shock. Twenty pigs were given endotoxin at various doses (0.063-16 microg kg(-1) h(-1)). Three non-endotoxaemic pigs served as controls. Two eicosanoids were measured in plasma (8-iso-PGF(2alpha), a free radical-mediated lipid peroxidation product, and 15-keto-dihydro-PGF(2alpha) a major metabolite of COX activity) and evaluated against the pathophysiological responses that occur during endotoxaemic shock. Endotoxin mediates an increase in both 8-iso-PGF(2alpha) and 15-keto-dihydro-PGF(2alpha). An increase in the endotoxin dose induced significant log-linear responses in 8-iso-PGF(2alpha) and 15-keto-dihydro-PGF(2alpha). Oxidative injury correlated to the TNF-alpha, IL-6, reductions in cardiac performance and to oxygen delivery and utilisation. COX-mediated inflammatory responses correlated to TNF-alpha, IL-6 and to reductions in arterial oxygen tension. Thus, oxidative injury and COX-mediated inflammation play a central role in the manifestation of endotoxaemic shock. Furthermore, formation of these eicosanoids on endotoxin-mediated alterations in pulmonary hypertension, oxygen delivery and oxygen utilisation seems to be independent of the administered endotoxin dose.     

Lipoxygenase inhibitors suppress formation of tumor necrosis factor in vitro and in vivo

Injection of endotoxin in D-galactosamine sensitized mice resulted in increased serum levels of tumor necrosis factor as determined in a fibroblast cytolysis assay. Concomitant injection of different lipoxygenase inhibitors decreased the titer of TNF. When the lipoxygenase inhibitors were tested in macrophage cultures stimulated with LPS, they prevented the production of TNF. Indomethacin, a blocker of cyclooxygenase was neither in vivo nor in vitro effective in the prevention of the endotoxin-induced synthesis of TNF. The involvement of superoxide anion in this effect was excluded by use of superoxide dismutase which did not influence the formation of TNF in macrophages.     

Anthocyans fail to suppress transformation of aryl hydrocarbon receptor induced by dioxin

Dioxins induce adverse effects through transformation of the cytosolic aryl hydrocarbon receptor (AhR). Our previous study found that flavones and flavonols at dietary levels suppress AhR transformation. In the present study, we investigated whether 20 anthocyans dissolved in trifluoroacetic acid (TFA)-MeOH suppressed AhR transformation in a cell-free system and in Hepa-1c1c7 cells. Although four compounds at 50 muM suppressed 0.1 nM 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced AhR transformation and their effects were dose-dependent in the cell-free system, they were ineffective at 0.5 muM, which is close to physiological concentration. Moreover, no anthocyan at 50 muM tested here suppressed 0.1 nM TCDD-induced AhR transformation in Hepa-1c1c7 cells. We also confirmed that protocatechuic acid and related compounds, which are possible metabolites of anthocyans, did not affect the transformation in the cell-free system. It is concluded that anthocyans are not suitable candidates for protection from dioxin toxicity.     

Identification of metabolites from type III F2-isoprostane diastereoisomers by mass spectrometry

F(2)-isoprostanes (F(2)-iPs) are prostaglandin (PG)-like products of non-enzymatic free radical-catalyzed peroxidation of arachidonic acid that are now widely used as indices of lipid peroxidation in vivo. Knowledge of the metabolic fate of F(2)-iPs in vivo is still scant, despite its importance for defining their overall formation and biological effects in vivo. Type III F(2)-iPs, which are diastereoisomers of cyclooxygenase-derived PGF(2alpha), may be metabolized through the pathways of PG metabolism. We therefore studied the in vitro metabolism of eight synthetic Type III F(2)-iP diastereoisomers in comparison with PGF(2alpha). We used gas chromatography-mass spectrometry and high performance liquid chromatography-electrospray-tandem mass spectrometry for structural identification of metabolites formed after incubation of the various compounds with isolated rat hepatocytes. PGF(2alpha) was metabolized to several known products, resulting from a combination of beta-oxidation, reduction of Delta(5) and/or Delta(13) double bonds, and 15-OH oxidation, plus other novel products deriving from conjugation with taurine of PGF(2alpha) and its metabolites. Of the eight F(2)-iP diastereoisomers, some were processed similarly to PGF(2alpha), whereas others showed peculiar metabolic profiles according to specific stereochemical configurations.These data represent the first evidence of biodegradation of selected Type III F(2)-iP isomers other than 8-epi-PGF(2alpha), through known and novel pathways of PGF(2alpha) metabolism. The analytical characterization of these products may serve as a basis for identifying the most significant products formed in vivo.     

Trichogramma releases in North Carolina cotton: why releases fail to suppress heliothine pests

Field studies were conducted in 1996 and 1997 to determine the fate of naturally oviposited F3 heliothine eggs in cotton plots treated with augmentative releases of Trichogramma exiguum Pinto & Platner and nontreated plots. Four cohorts of newly oviposited eggs (< 24 h old) were followed in 1996 and two cohorts in 1997. In 1996, mean +/- SD percent parasitism, estimated by in-field studies following the fate of naturally oviposited eggs, ranged from 7 +/- 7 to 61 +/- 8% in T. exiguum release plots and 0 +/- 0 to 35 +/- 13% in control plots. The mean +/- SD percent of eggs hatched in T. exiguum release plots ranged from 1 +/- 2 to 11 +/- 4% and 7 +/- 4 to 28 +/- 10% in control plots. In 1997, mean +/- SD percent egg parasitism ranged from 27 +/- 4 to 40 +/- 3% in T. exiguum release plots and 15 +/- 18 to 25 +/- 8% in control plots. The mean +/- SD percent of eggs hatched in T. exiguum release plots ranged from 7 +/- 3 to 12 +/- 2% and 18 +/- 6 to 28 +/- 8% in control plots. Despite increased parasitism and reduced egg hatch in T. exiguum release plots, overall, there was no significant difference in larval density (all instars combined) between T. exiguum release and control plots. Combined analysis of the heliothine larval populations and egg fate data revealed that the additional egg mortality produced by released T. exiguum was offset by lower larval mortality in release plots. Because of the occurrence of compensatory mortality, the egg stage of heliothines is not an appropriate target for biological control using Trichogramma wasp releases.     

Cyclooxygenase 1-dependent production of F2-isoprostane and changes in redox status during warm renal ischemia-reperfusion

The detrimental role of oxidative stress has been widely described in tissue damage caused by ischemia-reperfusion. A nonenzymatic, reactive oxygen species-related pathway has been suggested to produce 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)), an epimer of prostaglandin F(2alpha) (PGF(2alpha)), which has been proposed as an indicator of oxidative stress. Using an in vivo ischemia-reperfusion model in rat kidneys, we investigated intrarenal accumulation of 8-iso-PGF(2alpha) and PGF(2alpha). Both prostanoids accumulated in the ischemic kidney and disappeared upon reperfusion. In addition, a nonselective (acetylsalicylic acid) or selective cyclooxygenase (COX) 1 inhibitor (SC-560) completely abrogated the 8-iso-PGF(2alpha) and PGF(2alpha) formation in kidneys subjected to ischemia. COX2 inhibition had no effect on the production of these prostanoids. Therefore the two metabolites of arachidonic acid seemed to be produced via an enzymatic COX1-dependent pathway. Neither COX overexpression nor COX activation was detected. We also investigated renal glutathione, which is considered to be the major thiol-disulfide redox buffer of the tissue. Total and oxidized glutathione was decreased during the ischemic period, whereas no further decrease was seen for up to 60 min of reperfusion. These data demonstrate that a dramatic decrease in antioxidant defense was initiated during warm renal ischemia, whereas the 8-iso-PGF(2alpha) was related only to arachidonate conversion by COX1.     

Bone marrow mesenchymal stem cells suppress lymphocyte proliferation in vitro but fail to prevent graft-versus-host disease in mice

Several reports have suggested that mesenchymal stem cells (MSCs) could exert a potent immunosuppressive effect in vitro, and thus may have a therapeutic potential for T cell-dependent pathologies. We aimed to establish whether MSCs could be used to control graft-vs-host disease (GVHD), a major cause of morbidity and mortality after allogeneic hemopoietic stem cell transplantation. From C57BL/6 and BALB/c mouse bone marrow cells, we purified and expanded MSCs characterized by the lack of expression of CD45 and CD11b molecules, their typical spindle-shaped morphology, together with their ability to differentiate into osteogenic, chondrogenic, and adipogenic cells. These MSCs suppressed alloantigen-induced T cell proliferation in vitro in a dose-dependent manner, independently of their MHC haplotype. However, when MSCs were added to a bone marrow transplant at a MSCs:T cells ratio that provided a strong inhibition of the allogeneic responses in vitro, they yielded no clinical benefit on the incidence or severity of GVHD. The absence of clinical effect was not due to MSC rejection because they still could be detected in grafted animals, but rather to an absence of suppressive effect on donor T cell division in vivo. Thus, in these murine models, experimental data do not support a significant immunosuppressive effect of MSCs in vivo for the treatment of GVHD.     

The response of muscle interstitial F2-isoprostane (8-ISO-PGF2alpha) during dynamic muscle contractions in humans

8-Iso-prostaglandin F2alpha (8-iso-PGF2alpha) is a characteristic F2-isoprostane which is produced in humans via a free radical-catalysed lipid peroxidation mechanism of arachidonic acid, independent of the cycloxygenase pathway. The measurement of the plasma levels of 8-iso-PGF2alpha was shown to be the most reliable biochemical index of oxidant stress status in the human body. However, there is no reference in literature of local muscle interstitial 8-iso-PGF2alpha production during dynamic muscle contractions. The aim of the present study was to evaluate the response of 8-iso-PGF2alpha during intensive exercise with a cycle ergometer. Two microdialysis probes with CMA-60 microdialysis catheters were inserted into the vastus lateralis muscle of the right leg of six healthy male volunteers. After insertion, these microdialysis probes were attached to a perfusion pump that perfused ringer acetate solution at a rate of 0.3 microl/min. The dialysate fluid samples were collected: (a) during a 30 min rest period and (b) during a 30 min period of dynamic exercise with a cycle ergometer at 150 Watts. Our measurements showed that the levels of 8-iso-PGF2alpha in the interstitial fluid (IF) of the vastus lateralis muscle increase significantly during exercise (from 113.5 +/- 30.2 to 329.9 +/- 69.8 pg/ml, P = 0.05). In conclusion, dynamic muscle exercise produces a local increase of the IF levels of 8-iso-PGF2alpha due to local peroxidation injury of the contractive muscle. The microdialysis method is widely applied, easily repeated and it could contribute in evaluating the local lipid muscle peroxidation during intensive exercise.