OBJECTIVES: To study the possible interaction between ascorbic acid (AA) and oestradiol (E2) in postmenopausal women on hormone replacement therapy (HRT). METHODS: We studied 25 healthy postmenopausal women who had used percutaneous E2 gel at same dose for 10-12 months, at which time the plasma E2 concentrations were stabilized. The subjects were treated with 1000 mg of AA daily for 3 months and blood samples for assay of AA and E2 were taken at 0, 1 and 3 months. RESULTS: After 1 month of AA treatment, there was an overall increase of 20.8% in E2 levels in the group as a whole. Greater responses were seen in two subgroups. In women with initially the lowest plasma concentrations of AA (<70 micromol/l), there was an increase of 55% in plasma E2 levels which was close to significance (P=0.063). In another subgroup with initially the lowest E2 levels (<0.20 nmol/l) there was a marked and significant increase (from 0.13 to 0.26 nmol/l) in plasma E2 concentrations (P=0.028). CONCLUSIONS: Our results support early findings that AA may interact with oestrogen therapy. Possible interaction of AA with E2 at the level of antioxidation is discussed.

Despite convincing results of studies in vitro, less is known about the effects of antioxidants on in vivo redox balance in humans. We developed a novel parameter of in vivo redox balance, and studied it and its relation to dental infections in 51 patients on medication for coronary heart disease (CHD) and 39 random controls matched for age group, sex, social class and locality. In vivo redox balance was the ratio of plasma antioxidant capacity, as measured with radical-trapping assay, to neutrophil respiratory burst capacity, as measured with whole blood chemiluminescence assay. Dental infections were quantitated with four rating scales. CHD patients had higher values than controls. Patients on acetosalicylic acid (ASA), diuretics or beta blockers, but not the ones on calcium channel blocker, had significantly higher redox balance than non-users. Combination of calcium channel blockers and ASA was associated with redox balance similar to taking beta blockers or diuretics. Diuretics and ASA were independent determinants of redox balance in multivariate analyses. Redox balance did not correlate with severity of dental infections (Spearman's r 0.06 to 0.11). The results contrast experimental data indicating that calcium channel blockers are as antioxidants superior to other cardiovascular drugs. Total antioxidant capacity in parallel with oxygen species production capacity should be considered in attempts to solve the antioxidant paradox.

Many complications of prematurity have been suggested to result from free radical generation and an inadequacy of antioxidative capacity. We measured the plasma total peroxyl radical-trapping capability (TRAP) and concentrations of the main chain-breaking antioxidants contributing to it, i.e. uric acid, ascorbic acid, alpha-tocopherol, protein sulfhydryl groups and bilirubin, in 21 preterm infants with a mean birth weight of 1440 g and gestational age of 30 wk. The infants were divided into two groups according to their short-term outcome; the good outcome group (GOG)(N = 11) with no signs of morbidity and the poor outcome group (POG)(N = 10) with intraventricular haemorrhage and/or bronchopulmonary dysplasia and/or retinopathy. Arterial blood samples were obtained 3 and 10 days postpartum. TRAP was measured with a chemiluminescent method. As a comparison, venous blood samples from 13 adults (aged from 18 to 34) were used. At day 3 the poor outcome group had significantly higher TRAP than the good outcome or control group, mainly because of elevated uric acid concentration. Also the concentration of unidentified antioxidants was significantly lower in GOG. By day 10 the TRAP decreased substantially in both groups. However, from the components of TRAP, both ascorbate and the unidentified fraction decreased more in POG (p = 0.017 and 0.021, respectively). Furthermore in POG on day 10 urate concentration did not significantly differ from day 3 values. In conclusion, in preterm infants high TRAP was associated with high plasma uric acid concentration and a poor short-term prognosis.

Even though it is well established that oxygen-free radicals are the main mechanism responsible for the cytotoxicity produced during radiotherapy, the role of the human antioxidant defense system in clinical radiation oncology is still to be clarified. Changes in the human plasma total peroxyl radical trapping capacity (TRAP) and its individual components were followed during clinical radiotherapy for lung cancer. Sixteen patients receiving radical-aimed radiotherapy provided blood samples nine times during the treatment. Our hypothesis was that oxygen-free radical production increased by irradiation should decrease the plasma TRAP as a consequence of oxidative stress. Only a moderate reduction of the plasma TRAP was found during the therapy in the study group taken as a whole, but the development pattern of TRAP and its unidentified components were clearly different in those patients showing complete or partial response to the treatment and those in which the disease progressed unabated. Plasma ascorbate levels showed no significant changes during radiotherapy. A decrease in vitamin E concentrations was seen after 6 Gy (p=0.05). Uric acid concentrations increased towards the end of the radiotherapy in both response groups (p=0.02 at 50 Gy). In this study, 26.6% of the plasma TRAP was due to unidentified antioxidants (UNID).

The effects of substituted catechols (3-methylcatechol, 4-methylcatechol, 4-nitrocatechol, and guaiacol) and trihydroxybenzenes (pyrogallol, propyl gallate, 1,2,4-trihydroxybenzene, and 1,3,5-trihydroxybenzene) on the synthesis of prostaglandin (PG)E2 and leukotriene (LT)B4 were tested in human A23187-stimulated polymorphonuclear leukocytes. The effects were related to their peroxyl-radical-scavenging (antioxidant), superoxide-scavenging (antioxidant), and superoxide-generating (prooxidant) properties. In general, compounds with hydroxyl groups in the ortho position increased PGE2/LTB4 ratio, and compounds with hydroxyl groups in the meta position decreased PGE2/LTB4 ratio. Catechols, which have hydroxyl groups in the ortho position, were the most potent peroxyl radical and superoxide anion scavengers. Trihydroxybenzenes (pyrogallol, 1,2,4-trihydroxybenzene, and 1,3,5-trihydroxybenzene) generated superoxide, whereas dihydroxybenzenes did not. Thus, the positions and number of hydroxyl groups seem to be the most important properties determining the action of phenolic compounds on PGE2/LTB4 ratio and their antioxidant/prooxidant activities.

Previous evidence suggests that malignant tumors cause an oxidative burden to human antioxidative defense systems. We followed the plasma total radical-trapping antioxidant parameters (TRAP) and their main antioxidant components (alpha-tocopherol, uric acid, protein sulfhydryl groups, and unidentified antioxidant proportions) in 13 lung cancer patients and 7 control patients scheduled for thoracotomy. Plasma samples were collected 9 times during a 5 month follow-up period in the cancer patients. The objective of the study was to evaluate the effects of surgical removal of lung cancer on human plasma total antioxidant capacity. A significant reduction of plasma TRAP (period effect of ANOVA, p = 0.0006) and its components appeared in both groups during the first postoperative day. This decrease was due to reduction of ascorbate (p = 0.002) alpha-tocopherol (p = 0.0001) and urate (p = 0.05) concentrations. At 3 and 5 months after the surgical removal of the tumor there was an augmentation in plasma TRAP concentrations (p = 0.02, 3 months; p = 0.07, 5 months). This was mainly due to the increases in plasma yet as unidentified antioxidant components (UNID) and protein SH-groups. The data indicates that, first, thoracotomy itself causes a reduction in plasma TRAP during the early hours after operation, and secondly surgical removal of lung cancer increases plasma TRAP concentrations compared to the baseline values possibly reflecting the relief of oxidative stress caused by malignant tumors.

The nitric oxide (NO)-, superoxide anion (O2.-)- and peroxynitrite (ONOO-)-releasing properties of 1,2,3,4-oxatriazolium,5-amino-3-(3,4-dichlorophenyl)-chloride (GEA 3162) were characterized and compared with the known NO-donors 3-morpholino-sydnonimine (SIN-1) and S-nitroso-N-acetylpenicillamine. All the three compounds released NO in aqueous solutions in a dose-dependent manner as measured by ozone-chemiluminescence. GEA 3162 produced more NO than SIN-1, but less than S-nitroso-N-acetylpenicillamine during a 45 min incubation time. SIN-1 reduced nitro blue tetrazolium and the effect was inhibitable by superoxide dismutase. Reduction of nitro blue tetrazolium was not detected in the solutions of GEA 3162 and S-nitroso-N-acetylpenicillamine suggesting that SIN-1 but not GEA 3162 and S-nitroso-N-acetylpenicillamine release O2.- in their decomposition process. Formation of ONOO- in solutions of GEA 3162, SIN-1 and S-nitroso-N-acetylpenicillamine was estimated indirectly by measuring the formation of nitrotyrosine. The data indicate that ONOO- was produced in the presence of SIN-1 but not in solutions of GEA 3162 and S-nitroso-N-acetylpenicillamine. The results suggest that GEA 3162 produces negligible amounts of O2.- and ONOO- as compared to SIN-1. This adds the value of GEA 3162 as an useful tool in NO research and could well explain the earlier findings on the superior NO-like biological activity of oxatriazole derivatives as compared to SIN-1.

The effect of a new nitric oxide (NO) donor, a meso-ionic 3-aryl substituted oxatriazole-5-imine derivative, GEA 3162 was studied on constant flow-perfused ischaemic Langendorff rat heart. The perfusion was kept constant at a rate of 16 mL min-1. Ischaemia was induced by a low flow rate of 0.8 mL min-1 for 30 min, and was followed by a 40-minute reperfusion. In the first set of experiments the effects of GEA 3162-infusion were examined on perfusion pressure, left ventricular pressure, heart rate and left ventricular dP/dt. GEA 3162 infusion did not affect the pre-ischaemic maximum of left ventricular pressure. During reperfusion, maximal left ventricular pressure, maximal and minimal dP/dt values in the GEA 3162-treated group significantly exceeded those of the untreated controls (by 19.3, 36.0 and 18.0%, respectively). During reperfusion, perfusion pressure increased continuously in the control group indicating an increasing coronary resistance, but it was kept at a continuous low level with GEA 3162 treatment. In a second set of experiments bradykinin was infused in order to test the endothelial function before ischaemia and during late reperfusion. Bradykinin elicited significant vasodilation in the control group during reperfusion, meanwhile it did not cause further change in coronary resistance in the GEA 3162-infused group. We suggest, that GEA 3162 may have a protective effect on isolated rat heart in ischaemia and reperfusion, that results in an improved cardiac performance compared with untreated hearts.

Previous observations have suggested that low intakes of fluoride prevent pathological calcifications of internal organs, including the aortic wall, in experimental animals, fed a basically low magnesium diet. Our group found recently that fluoride has some potentially preventive effect against atherosclerotic serum lipid profiles in genetically hypercholesterolaemic rats. To study whether the apparently positive potential of fluoride against atherosclerosis is also reflected in aortic tissue, through its well known activation of adenylate cyclase, the aortic cAMP content of the rats used in our recent study was determined. Out of a total of 56 male RICO rats, mean weight 160 g, the control group C was fed an adequate diet, with 44% sucrose, a magnesium content of 883 p.p.m. and with 0.5% cholesterol. Group D had the same diet as group C except that the magnesium content was reduced to 200 p.p.m. Group E had the same diet as group D but with the fluoride content elevated from 1.9 to 12 p.p.m. Group G had the same diet as group E but with the magnesium content elevated from 200 to 300 p.p.m. After a feeding period of 6 weeks, the aortas of the animals were removed, cleaned and kept at -70 degrees C until analysed. The mean cAMP content of the aortas, measured by radioimmunoassay, in groups C, D E and G was 439, 546, 681, and 1394 mumol mg-1 protein, respectively. In group G only, the cAMP content was significantly higher than that of the other groups (p < 0.001). The mean calcium and magnesium contents of the aortas of different groups did not significantly differ from each other. Thus in RICO rats, fed a high-sugar low-magnesium diet with cholesterol, supplementation of the diet with a small amount of fluoride elevates the cAMP content of the aorta, provided that the intake of Mg is not very low.

Evidence is rapidly accumulating that oxidative modification of low density lipoprotein (LDL) may play an important role in the pathogenesis of atherosclerosis. In this study we measured the total peroxyl radical trapping capacity of human plasma LDL phospholipids (TRAPLDL) with a luminescent method. The study was carried out with 70 healthy volunteers, aged 28-77. In males an age-related decrease in TRAPLDL was observed. In the age group under 50 years the mean TRAPLDL was 31.36 +/- 1.45 pmol peroxyl radicals/nmol Pi; among those over 50 years it was significantly lower at 26.67 0.94 pmol/nmol Pi. As regards the components of TRAPLDL, the concentration of LDL-ubiquinol did not change and a non-significant decrease in the LDL-tocopherol concentration was detected with age. In females, the mean TRAPLDL, LDL-ubiquinol-10 and tocopherol concentrations did not differ between the age groups. When 17 of the participants were given coenzyme Q10 (Q10) supplementation, 100 mg/day, a highly significant increase in LDL-ubiquinol concentration was detected. Our results indicate that LDL antioxidant defenses tend to decrease with age in the Finnish male population. The decline is most significant in males under 50 years; in older age groups the values remain stable at a low level. Q10 supplementation doubles the number of ubiquinol-10-containing LDL molecules and may therefore have an inhibitory effect on LDL oxidation.