Comparative inhibition of tetrameric carbonyl reductase activity in pig heart cytosol by alkyl 4-pyridyl ketones.

Context And Objective: The present study is to elucidate the comparative inhibition of tetrameric carbonyl reductase (TCBR) activity by alkyl 4-pyridyl ketones, and to characterize its substrate-binding domain.

Materials And Methods: The inhibitory effects of alkyl 4-pyridyl ketones on the stereoselective reduction of 4-benzoylpyridine (4-BP) catalyzed by TCBR were examined in the cytosolic fraction of pig heart.

Results: Of alkyl 4-pyridyl ketones, 4-hexanoylpyridine, which has a straight-chain alkyl group of five carbon atoms, inhibited most potently TCBR activity and was a competitive inhibitor.

Sexual dimorphism of cadmium-induced toxicity in rats: involvement of sex hormones.

The toxic effect of cadmium varies with sex in experimental animals. Previous studies have demonstrated that pretreatment of male Fischer 344 (F344) rats with the female sex hormone progesterone markedly enhances the susceptibility to cadmium, suggesting a role for progesterone in the sexual dimorphism of cadmium toxicity. In the present study, we attempted to further elucidate the mechanism for sex differences in cadmium-induced toxicity in F344 rats.

Possible mechanism of superoxide formation through redox cycling of plumbagin in pig heart.

The purpose of this study is to elucidate the possible mechanism of superoxide formation through redox cycling of plumbagin (PLG) in pig heart. Of four 1,4-naphthoquinones tested in this study, PLG was most efficiently reduced in the cytosolic fraction of pig heart. On the other hand, lawsone (LAS) was little reduced.

Genetic background of resistance to cadmium-induced testicular toxicity in inbred Wistar-Imamichi rats.

We have previously reported that inbred Wistar-Imamichi (WI) rats are highly resistant to cadmium (Cd)-induced testicular toxicity compared with inbred Fischer 344 (F344) rats. The present study was to elucidate the genetic background of resistance to Cd-induced testicular toxicity in WI rats. The genetic analysis of susceptibility to Cd-induced testicular toxicity was conducted by using Cd-resistant WI and Cd-sensitive F344 strains as the parental rats and by using the testicular hemoglobin level as the indicator.

Differential mechanisms for the inhibition of human cytochrome P450 1A2 by apigenin and genistein.

The inhibitory effects of flavonoids on the human cytochrome P450 1A2 (CYP1A2) were examined. Among flavonoids tested, galangin, kaempferol, chrysin, and apigenin were potent inhibitors. Although apigenin belonging to flavones and genistein belonging to isoflavones are similar in the chemical structures, the inhibitory potencies for CYP1A2 were distinguished markedly between these two flavonoids.

Strain difference of cadmium-induced testicular toxicity in inbred Wistar-Imamichi and Fischer 344 rats.

Previously, we reported that Wistar-Imamichi (WI) rats are highly resistant to cadmium (Cd)-induced lethality and hepatotoxicity compared to Fischer 344 (F344) rats. Since the testes are one of the most sensitive organs to acute Cd toxicity, we examined possible strain-related differences in Cd-induced testicular toxicity between inbred WI and F344 rats. Rats were treated with a single dose of 0.

[Structure and function of peroxisomal tetrameric carbonyl reductase].

In this paper, the structure and function of a new tetrameric carbonyl reductase (TCR) is reviewed. TCRs were purified from rabbit and pig heart, using 4-benzoylpyridine as a substrate. Partial peptide sequencing and cDNA cloning of rabbit and pig TCRs revealed that both enzymes belonged to the short-chain dehydrogenase/reductase family and that their subunits consisted of 260 amino acid residues.

Characterization of human DHRS4: an inducible short-chain dehydrogenase/reductase enzyme with 3beta-hydroxysteroid dehydrogenase activity.

Human DHRS4 is a peroxisomal member of the short-chain dehydrogenase/reductase superfamily, but its enzymatic properties, except for displaying NADP(H)-dependent retinol dehydrogenase/reductase activity, are unknown. We show that the human enzyme, a tetramer composed of 27kDa subunits, is inactivated at low temperature without dissociation into subunits. The cold inactivation was prevented by a mutation of Thr177 with the corresponding residue, Asn, in cold-stable pig DHRS4, where this residue is hydrogen-bonded to Asn165 in a substrate-binding loop of other subunit.

Molecular basis for peroxisomal localization of tetrameric carbonyl reductase.

Pig heart peroxisomal carbonyl reductase (PerCR) belongs to the short-chain dehydrogenase/reductase family, and its sequence comprises a C-terminal SRL tripeptide, which is a variant of the type 1 peroxisomal targeting signal (PTS1) Ser-Lys-Leu. PerCR is imported into peroxisomes of HeLa cells when the cells are transfected with vectors expressing the enzyme. However, PerCR does not show specific targeting when introduced into the cells with a protein transfection reagent.

Strain difference of cadmium accumulation by liver slices of inbred Wistar-Imamichi and Fischer 344 rats.

Strain difference in the accumulation of cadmium (Cd) by liver slices was examined in inbred Cd-resistant Wistar-Imamichi (WI) and Cd-sensitive Fischer 344 (F344) rats. The accumulation of Cd by liver slices of WI rats was significantly lower than that of F344 rats, suggesting strain-related differences in the transport of Cd into the liver cells of these two rat strains. In addition, a similar strain difference was observed in the accumulation of zinc (Zn) by liver slices from WI and F344 rats.

(R)-ACX, a pancreatic beta-cell selective sulfonylurea, does not aggravate myocardial ischemia-reperfusion damage.

The organ selectivity and the effect on myocardial ischemia-reperfusion injury of (R)-acetoxyhexamide ((R)-ACX), a novel sulfonylurea, were examined. (R)-ACX, as well as glibenclamide, concentration-dependently stimulated insulin release from INS-1 cell, a cell line derived from pancreatic beta-cells. The potency of (R)-ACX was about 1/10 of that of glibenclamide.

Inhibitory effects of diesel exhaust components and flavonoids on 20alpha-hydroxysteroid dehydrogenase activity in mouse tissues.

The inhibitory effects of diesel exhaust components and flavonoids on 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) activity were examined in cytosolic fractions from the liver, kidney and lung of male mice. 9,10-Phenanthrenequinone (9,10-PQ) and 1,2-naphthoquinone (1,2-NQ), which are contained in diesel exhaust particles (DEPs), potently inhibited 20alpha-HSD activity in liver cytosol. 9,10-PQ also inhibited the enzyme activity in lung cytosol.

Characterization of an oligomeric carbonyl reductase of dog liver: its identity with peroxisomal tetrameric carbonyl reductase.

Dog liver contains an oligomeric NADPH-dependent carbonyl reductase (CR) with substrate specificity for alkyl phenyl ketones, but its endogenous substrate and primary structure remain unknown. In this study, we examined the molecular weight and substrate specificity of the enzyme purified from dog liver. The enzyme is a ca.

Several distinct enzymes catalyze 20alpha-hydroxysteroid dehydrogenase activity in mouse liver and kidney.

The effects of flavonoids and quinones on NADPH- and NADH-dependent 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) activities were examined in cytosolic fractions from the liver and kidney of mice. Judging from the data for the inhibition of NADPH- and NADH-dependent 20alpha-HSD activities by flavonoids and quinones, enzyme catalyzing renal NADPH-dependent 20alpha-HSD activity was found to be distinct from enzyme(s) catalyzing hepatic NADPH- and NADH-dependent 20alpha-HSD activities. Sulfobromophthalein (SBP) had little ability to inhibit hepatic NADPH-dependent 20alpha-HSD activity and bromophenol blue (BPB) exhibited a weak activation against the enzyme activity, whereas SBP and BPB were potent and moderate inhibitors, respectively, of hepatic NADH-dependent 20alpha-HSD activity.

Inhibition of carbonyl reductase activity in pig heart by alkyl phenyl ketones.

The inhibitory effects of alkyl phenyl ketones on carbonyl reductase activity were examined in pig heart. In this study, carbonyl reductase activity was estimated as the ability to reduce 4-benzoylpyridine to S(-)-alpha-phenyl-4-pyridylmethanol in the cytosolic fraction from pig heart (pig heart cytosol). The order of their inhibitory potencies was hexanophenone > valerophenone > heptanophenone > butyrophenone > propiophenone.

Stereoselective reduction of 4-benzoylpyridine in the heart of vertebrates.

The stereoselectivity in the reduction of 4-benzoylpyridine (4-BP) was examined in the cytosolic fractions from the heart of 9 vertebrates (pig, rabbit, guinea pig, rat, mouse, chicken, soft-shelled turtle, frog and flounder). 4-BP was stereoselectively reduced to S(-)-alpha-phenyl-4-pyridylmethanol [S(-)-PPOL] in the cytosolic fractions from the heart of pig, rabbit and guinea pig. However, of mammalian heart cytsol tested, only rat heart cytosol had little ability to reduce stereoselectively 4-BP.

Crystallization and preliminary X-ray crystallographic studies of pig heart carbonyl reductase.

Pig heart carbonyl reductase (PHCR), which belongs to the short-chain dehydrogenase/reductase (SDR) family, has been crystallized by the hanging-drop vapour-diffusion method. Two crystal forms (I and II) have been obtained in the presence of NADPH. Form I crystals belong to the tetragonal space group P4(2), with unit-cell parameters a = b = 109.

Effects of quinones and flavonoids on the reduction of all-trans retinal to all-trans retinol in pig heart.

We have recently purified a tetrameric carbonyl reductase from the cytosolic fraction of pig heart (pig heart carbonyl reductase). Since pig heart carbonyl reductase efficiently reduces all-trans retinal as the endogenous substrate, it probably plays an important role in retinoid metabolism in the heart. The purpose of the present study was to evaluate the inhibitory effects of quinones and flavonoids on the reduction of all-trans retinal to all-trans retinol catalyzed by pig heart carbonyl reductase, using pig heart cytosol.

A possible mechanism of resistance to cadmium toxicity in male Long-Evans rats.

The susceptibility to cadmium (Cd)-induced toxicity in male Long-Evans (LE) rats was compared with that in male Fischer 344 (Fischer) and Wistar-Imamichi (WI) rats, which are sensitive and resistant, respectively, to Cd toxicity. All rats of the LE and WI strains survived for 7 days after the treatment with a toxic dose of Cd (6.5mg/kg b.

Characteristics and inhibition by flavonoids of 20alpha-hydroxysteroid dehydrogenase activity in mouse tissues.

Progesterone was stereoselectively reduced to a metabolite 20alpha-hydroxy-4-pregnen-3-one in the cytosolic fraction from the liver of male mice, indicating that the reduction of progesterone is catalyzed by 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD). The cytosolic 20alpha-HSD activity was observed not only in the liver, but also in the kidney and lung. In liver cytosol, both NADPH and NADH were effective as cofactors for 20alpha-HSD activity, although NADPH was better than NADH for the enzyme activity.

Involvement of carbonyl reductase in superoxide formation through redox cycling of adrenochrome and 9,10-phenanthrenequinone in pig heart.

The effects of adrenochrome, a metabolite of epinephrine (adrenaline), and 9,10-phenanthrenequinone (PQ), a component of diesel exhaust particles, on the stereoselective reduction of 4-benzoylpyridine (4-BP) were examined in pig heart cytosol. PQ was a potent inhibitor for the 4-BP reduction, while adrenochrome was a poor inhibitor. A similar result was observed in the effects of adrenochrome and PQ on the reduction of all-trans retinal.

Inhibitory effects of flavonoids on the reduction of progesterone to 20alpha-hydroxyprogesterone in rat liver.

The first aim of this study is to characterize the reduction of progesterone in rat liver. Progesterone was mainly reduced to 20alpha-hydroxyprogesterone in the cytosolic fraction of rat liver. The amount of 20alpha-hydroxyprogesterone formed from progesterone in the cytosolic fraction was significantly larger in the males than in the females and this enzyme reaction proceeded not only in the presence of NADPH, but also in the presence of NADH.

Differential pharmacokinetics of acetohexamide in male Wistar-Imamichi and Sprague-Dawley rats: role of microsomal carbonyl reductase.

Acetohexamide (AH) is reduced to its alcohol metabolite by carbonyl reductase. We have previously shown that carbonyl reductase present in the liver microsomes of rats is a male-specific and androgen-dependent enzyme. In the present study, the role of microsomal carbonyl reductase in the pharmacokinetics of AH was examined in male Wistar-Imamichi (WI) and Sprague-Dawley (SD) rats after its intravenous administration.

Effects of chelating agents on distribution and excretion of terbium in mice.

When terbium chloride (TbCl(3)) was intravenously injected into mice, terbium (Tb) was mainly distributed into the spleen, lung, and liver. Thus, the effects of five chelating agents on the distribution of Tb to the spleen, lung, and liver of mice were examined. The treatments with diethyldithiocarbamate (DDTC), N-p-methoxybenzyl-D-glucamine dithiocarbamate (MeOBGD) and 2,3-dimercaptopropanol (BAL) reduced the content of Tb in the spleen.

Protection from spontaneous hepatocellular damage by N-benzyl-d-glucamine dithiocarbamate in Long-Evans Cinnamon rats, an animal model of Wilson's disease.

The Long-Evans Cinnamon (LEC) rat is a mutant strain that accumulates excessive tissue copper (Cu) and models the clinical symptoms and biological features of Wilson's disease in humans. We compared the effects of three metal chelating agents, N-benzyl-d-glucamine dithiocarbamate (BGD), d-penicillamine (D-PEN), and triethylenetetramine (TETA), on the biliary and urinary excretions of Cu using LEC rats. The animals were treated ip with each chelating agent (1 mmol/kg body weight) and then the bile and urine samples were collected for 3 h.