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Cobalt(ii)-tetraphenylporphyrin (CoVpp)-fixed glassy carbon (GC) electrodes were prepared using 4-aminopyridine (pyNH2) in the form of Colltpp-pyNH-CO/GC, which were active for electroreduction of C 0 2 to CO at potentials 100 mV more positive than water-soluble Coil porphyrins, and the overall turnover number of Coiltpp for CO production exceeded 105.Metalloporphyrins have been reported to be active as catalysts in the electroreduction of C 0 2 in aqueous' and nonaqueous2 media. In aqueous media, water-soluble CoIItetraphenylporphyrin sulphonate and CoTTrneso-tetracarboxyphenylporphyrin have been reported to be catalytically active for the electroreduction of C 0 2 . Pyridine (py) is reported to coordinate at the axial position of planar CoII(sa1en) (H2salen = bissalicylideneethylenediamine) and stabilizes C 0 2 in the opposite coordination site.3 In the present work, we attempted to obtain a CoIItpp-py (tpp = tetraphenylporphyrin) complex-fixed electrode by applying the water-insoluble CoIItpp on glassy carbon (GC) substrate plates modified initially with 4-aminopyridine (pyNH2). 4-Aminopyridine is expected not only to immobilize CoIItpp on the G C electrode, but also to provide the CoIItpp-fixed GC electrode with new properties.CoIItpp-pyNH-CO/GC (I) was prepared as follows Glassy carbon (GC) plates (Tokai GC-30, 27 mm x 5 mm, 1 mm thick) were subjected to anodic oxidation in 0.5 mol dm-3 H2S04, and refluxed in SOC12 for 24 h, for chlorination as COCl/GC. The electrodes were then immersed in 4-aminopyridine-saturated benzene solution for 24 h at room temperature to produce pyNH-CO/GC (11). Finally, the electrodes were refluxed in a 0.6 mmol dm-3 CoIItpp solution in benzene for 24 h to produce I.The fixation of 4-aminopyridine was confirmed by the diffuse reflectance FT IR spectrum of 11, which showed a peak at 1665 cm-1 due to C=O stretching of the -CO-NH-amide group together with pyridine ring C=C and C=N stretching peaks at 1610 and 1537 cm-1, respectively. These results showed that 4-aminopyridine was fixed in the form of pyNH-CO/GC. Fig. l(a) shows the diffuse reflectance UV-VIS spectrum of I, together with spectra of ( b ) CoIItpp and (c) CoIItpp-py in CH2C12 for comparison. Spectra ( a ) and (c) show the Soret band at 440 nm, whereas that of ( b ) is at 420 nm. These spectra indicated that Co**tpp was fixed as the pyridine complex, CoIItpp-py, and the electron density of the central ColI ions of I was increased by the pyridine 1igand.s Fig. 2 shows cyclic voltammograms (CV) of I in standard phosphate buffer solution at pH 6.86 saturated with He or C02. No CoIItpp/CoItpp redox peak was observed, but this is probably due to the small amount of CoIItpp distributed on the electrode which has a high roughness factor (3 x 103). The surface concentration of CoIItpp of (10-12 mol cm-2; apparent surface area) was evaluated by ESCA. A pronounced increase of the cathodic current was observed at potentials more negative than -0.95 V [vs. saturated calomel electrode (SCE)] in C02-saturated solution, this increase st...

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D-Mannitol, one of the main phytochemicals of the edible Tamogi-take mushroom (Pleurotus cornucopiae), was found to inhibit an angiotensin I converting enzyme (ACE). The antihypertensive effect of D-mannitol and a hot water extract of Tamogi-take mushroom was demonstrated in spontaneously hypertensive rats (SHR) by oral administration.

Exposure of pubertal rats to di-(2-ethylhexyl) phthalate (DEHP) for 14 days was reported to result in reduced testosterone (T) biosynthesis by altering androstenedione 17beta-hydroxysteroid dehydrogenase (17beta-HSD) activity. However, our study indicated that shorter period exposure of DEHP (100 or 1000 mg/kg for 5 days) to 4-week-old male rats did not affect the activity of 17beta-HSD, the rate-limiting enzyme of T biosynthesis in the testis. Testosterone 5alpha-reductase (T5alpha-R) activity in the testis was significantly enhanced, while aromatase mRNA was significantly reduced by increasing doses of DEHP. The expressions of cytochrome P450 (CYP) isoforms, CYP2C11 and CYP3A, in the testis increased along with their enzymatic activities, T16alpha- and T6beta-hydroxylation, respectively. Thus, the current study clearly indicates that the short period exposure to DEHP alters T metabolism through altering activities of T5alpha-R, aromatase and CYP2C11/3A2 in the testis of prepubertal rats, and that they are more sensitive marker enzymes to the DEHP exposure than those of biosynthetic enzymes of T from androstenedione.

Fibrates, hypolipidemic drugs, have been reported to suppress the metabolic activities of cytochrome P450 1A1 and 1A2 in rats but the mechanism has not been elucidated. In the present study we tested the hypothesis that the inhibitory effect of fibrates on arylhydrocarbon receptor (AhR) function may be due to their stimulatory effects on PPARalpha. Sudan III (S.III) treatment induced CYP 1A1 and CYP 1A2 protein expression, mRNA and their metabolic activities, methoxyresorufin-O-demethylase (MROD) and ethoxyresorufin-O-deethylase (EROD), in Wistar rats higher than those in the control. Co-treatment of rats with S.III and clofibric acid (CA) caused a 40-50% decrease in the induced levels of CYP1A1 and CYP1A2 protein, mRNA expression and their metabolic activities and reduced AhR protein expression. When we treated HepG2 cells with S.III and/or CA, no suppressive effect on S.III-induced CYP1A1 protein expression due to CA was found. HepG2 cells were transiently transfected with increasing concentrations of PPARalpha mammalian expression vector and exposed to the same treatment. CA co-treatment with S.III decreased AhR protein and S.III-induced CYP1A1 protein expression with increasing dose of PPARalpha transfected into HepG2 cells. Our results demonstrate that the suppressive effect of fibrates on CYP1A is PPARalpha-dependent and suggest that PPARalpha has an inhibitory effect on AhR function.

Peroxynitrite formed by the reaction of superoxide and nitric oxide is a highly reactive species with a role in various pathological processes such as cancer, chronic inflammation, and cardiovascular and neurological diseases. In the present study, the effect of the carotenoids, lycopene and β-carotene, on peroxynitrite-mediated modifications in plasmid DNA as well as cellular DNA and proteins were investigated. In pUC18 plasmid DNA, these carotenoids strongly inhibited DNA strand breaks caused by peroxynitrite generated from 3-morpholinosydnonimine (SIN-1). SIN-1 was also used to determine effects on DNA damage and protein tyrosine nitration in Chinese hamster lung fibroblasts. SIN-1 dose-dependently increased nitration of proteins in cells above basal levels as determined by western blotting. This nitration was inhibited in the presence of the uric acid as well as lycopene. Physiological concentrations (0.31-10 μM) of lycopene and β-carotene also had protective effects on DNA damage, as measured by the comet assay. Lycopene significantly reduced DNA damage particularly, in the median range of concentrations (2.5 μM).The protective effects of lycopene and β-carotene could be due to their scavenging of reactive oxygen (ROS) and/or nitrogen species (RNS) as they reduce the amount of intracellular ROS/RNS produced following treatment with SIN-1 by as much as 47.5 and 42.4 %, respectively. The results obtained in this study suggest that carotenoids may alleviate some of the deleterious effects of peroxynitrite and possibly other reactive nitrogen species as well in vivo.