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Biomedical subjects

R Kato

Publications and source records attributed to R Kato.

At least 469 records · Page 26Linked to original sources
PubMed1987

Staurosporine, a potent protein kinase C inhibitor, fails to inhibit 12-O-tetradecanoylphorbol-13-acetate-caused ornithine decarboxylase induction in isolated mouse epidermal cells.

Staurosporine, a most potent protein kinase C inhibitor, actually inhibited protein kinase C activity obtained either from cytosol or particulate fraction of mouse epidermis. Staurosporine at the concentrations which exert protein kinase C inhibition, however, failed to inhibit, but markedly augmented 12-O-tetradecanoylphorbol-13-acetate (TPA)-caused ornithine decarboxylase (ODC) induction in isolated mouse epidermal cells. Staurosporine by itself induced ODC activity as TPA does. Mechanism of ODC induction seems different between these two compounds. Another protein kinase C inhibitor, H-7, inhibited both staurosporine- and TPA-caused ODC induction.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1987

Studies on in vitro antipyrine metabolism by 13C,15N double labeled method.

The capacities of forms of cytochrome P-450 to oxidize antipyrine were compared. An isotope dilution gas chromatography/mass spectrometry/selected ion monitoring assay was developed to quantify the three main metabolites, norantipyrine, 3-hydroxymethylantipyrine and 4-hydroxyantipyrine. 13C,15N-Double labeled antipyrine was used as a substrate and the metabolites were analyzed as their trimethylsilyl derivatives. Among forms of cytochrome P-450 examined, a male-specific form of P-450, namely P-450-male, showed higher activity to form all the three metabolites. The other forms were responsible only for the formation of norantipyrine and 4-hydroxyantipyrine. The activities of liver microsomes from untreated male and female rats and rats treated with phenobarbital, 3-methylcholanthrene or polychlorinated biphenyl were expressed dependent on the activities of forms of cytochrome P-450 examined.

Animals↗
PubMed1987

Suppression of levels of phenobarbital-inducible rat liver cytochrome P-450 by pituitary hormone.

The effect of pituitary factor on the constitutive and inducible levels of hepatic phenobarbital (PB)-inducible major cytochrome P-450, P-450b and P-450e, in male and female rat livers was studied by immunoblot analyses. Although only trace amounts (approximately 4 pmol/mg protein) of P-450b and P-450e were detected in untreated adult rats, hypophysectomy increased the contents of P-450b and P-450e 58- and 14-fold, respectively, in male rats and 118- and 30-fold, respectively, in female rats. The increases were also observed in treatment with dexamethasone, which suppressed the pituitary function. Treatment with PB increased more effectively the hepatic contents of P-450b and P-450e, but their contents were still 4-fold higher in the male than the female. Treatment of hypophysectomized female rats with PB increased the contents of P-450b and P-450e 4-fold higher than the contents in PB-treated nonhypophysectomized female rats. Consequently, the sex-related difference in their contents was reduced less than 1.4-fold in the hypophysectomized rats treated with PB. Similar results were also obtained from the quantitation of microsomal O-pentylresorufin O-depentylation and testosterone 16 beta-hydroxylation. Either intermittent injection or continuous infusion of human growth hormone, but not of ovine prolactin, into hypophysectomized male and female rats decreased the contents of both cytochromes. These results indicate that growth hormone acts as a repressive factor for the constitutive and inducible levels of P-450b and P-450e in a manner different from the regulation of P-450-male and P-450-female.

Aging↗
PubMed1987

Effects of flecainide on the cellular electrophysiology of neonatal and adult cardiac fibers.

The acute cellular electrophysiologic actions of flecainide acetate on isolated neonatal and adult canine ventricular myocardium and Purkinje fibers were evaluated with standard microelectrode techniques. Flecainide, 0.1 to 10.0 micrograms/ml, produced concentration-dependent decreases in action potential amplitude, overshoot, and phase O Vmax of adult ventricular myocardium and Purkinje fibers. The greatest effects were on Vmax. Neonatal action potential characteristics were affected to a lesser degree by flecainide. Flecainide had disparate effects on myocardial and Purkinje fiber repolarization and refractoriness. In adult ventricular myocardium, action potential duration (APD) and effective refractory period (ERP) increased progressively with drug concentration. APD and ERP were increased to a lesser degree in neonatal myocardium. In adult Purkinje fibers, APD decreased progressively with increasing flecainide concentrations. ERP decreased at 0.1 and 1.0 microgram/ml, but returned to control values at 10.0 micrograms/ml. APD and ERP of neonatal Purkinje fibers responded to a lesser degree. At faster stimulation frequencies (2 to 4 Hz), flecainide produced significant frequency-dependent decreases in Vmax in adult Purkinje fibers. Such use-dependency was not evident in neonatal fibers. These data indicate a significantly lower sensitivity of immature cardiac tissues to the electrophysiologic effects of flecainide.

Action Potentials↗
PubMed1987

Genetic analysis of hypothermia induced by morphine in two strains of inbred mice.

The degree of hypothermia elicited by morphine was greater in DBA/2 than C57BL/6 strain mice of both sexes. Hypothermia elicited by morphine was antagonized by naloxone in both strains of mice, suggesting the involvement of opioid receptors. To examine the role of genetic factors in the strain difference of morphine-induced hypothermia, the effect of morphine on changes in the rectal temperature was studied in the 6 generations of male mice, including the 2 inbred strains, P1 (DBA/2) and P2 (C57BL/6), their F1 and F2 hybrids, and 2 backcrosses, B1 (F1 X P1) and B2 (F1 X P2). The order of mean temperature decrease determined 40 min after 20 mg/kg morphine injection was P1 greater than B1 greater than F1 = F2 greater than B2 greater than P2. There was no maternal effect on the morphine responses of the F1 generation. Biometrical analysis revealed that DBA/2 (P1) is partially dominant over C57BL/6 (P2) and contribution of polygenes was suggested.

Animals↗
PubMed1987

Purification of human liver cytochrome P-450 catalyzing testosterone 6 beta-hydroxylation.

Two forms of cytochrome P-450 (P-450 human-1 and P-450 human-2) have been purified from human liver microsomes to electrophoretic homogeneity. P-450 human-1 and P-450 human-2 differ in their apparent molecular weights (52,000 and 56,000, respectively) and Soret peak maxima in the CO-binding reduced difference spectrum (447.6 and 450.3 nm, respectively). In the reconstituted system using rat liver NADPH-cytochrome c (P-450) reductase, P-450 human-2 more effectively oxidized benzo(a)pyrene (80-fold), ethylmorphine (2-fold), and 7-ethoxycoumarin (2-fold) than did P-450 human-1. However, P-450 human-1 showed higher testosterone 6 beta-hydroxylase activity, and the activity was markedly increased by the inclusion of cytochrome b5 or spermine in the reconstituted system. Antibodies raised against P-450 human-1 inhibited more than 80% of microsomal testosterone 6 beta-hydroxylase activity in human liver. Immunoblotting analysis using anti-P-450 human-1 IgG revealed a single immuno-staining band near Mr 52,000 in all human liver samples examined. The amount of immunochemically determined P-450 human-1 varied in parallel with the testosterone 6 beta-hydroxylase activity in human liver. These results indicate that P-450 human-1 is a major form of cytochrome P-450 responsible for microsomal testosterone 6 beta-hydroxylation. Thus, this paper is the first report on human cytochrome P-450 responsible for testosterone 6 beta-hydroxylation, which is the major hydroxylation pathway in human liver microsomes.

Adolescent↗
PubMed1987

Nucleotide sequence of a human liver cytochrome P-450 related to the rat male specific form.

P-450 human-2 is a human cytochrome P-450 that is immunochemically related to a constitutive male-specific cytochrome P-450 (P-450-male) and the phenobarbital-inducible P-450b/e in rat liver. By screening a human liver cDNA library in bacteriophage lambda gt11, we isolated a clone with an insert length of 1,847 bases (pHY13). The clone was sequenced and shown to code for a protein of 487 amino acids. The N-terminal 11-amino-acid sequence was in agreement with the protein sequence of P-450 human-2. The nucleotide sequence of pHY13 showed less than 50% similarity with those of human cytochrome P-450s, pHP-450(1), HLp, P-450NF, P1-450 4, and P3(450), but the nucleotide sequence of pHY13 is 80% similar to the reported sequence of rat cytochrome P-450, P-450(M-1). In addition, the coding sequence of pHY13 showed close similarity to that of MP-8, which was recently reported as the sequence corresponding to human cytochrome P-450MP, although no apparent similarity was observed in their 3' non-coding sequences except for the first 75 bases and the expected length of the complete sequences. These results, together with the immunochemical data, indicate that P-450 human-2 is closely related, but not identical, to P-450MP, and may belong to the category of developmentally regulated constitutive cytochrome P-450s.

Amino Acid Sequence↗
PubMed1987

Drug oxidation activities of horseradish peroxidase, myoglobin and cytochrome P-450cam reconstituted with synthetic hemes.

Drug oxidations by horseradish peroxidase (HRP), myoglobin (Mb) and cytochrome P-450cam (P-450cam) reconstituted with synthetic hemes were studied in comparison with a form of cytochrome P-450 purified from liver microsomes of polychlorinated biphenyl (PCB)-treated rats. N,N-Dimethylaniline (DMA) and 7-isopropoxycoumarin were hardly dealkylated by the heme-substituted proteins in the presence of NADPH-cytochrome c (P-450) reductase and NADPH, while substantial activity of this kind was observed in the presence of hydrogen peroxide or cumene hydroperoxide as oxygen donors. Specific activity varied, depending on the substrates, oxygen donors, heme derivatives and apoproteins employed. Very high levels of activity were observed in hydrogen peroxide-dependent DMA N-demethylation with HRP substituted with certain hemes. The highest level of activity was about two hundred times as high as that of rat liver cytochrome P-450. The relationship between such activity and the chemical structure of heme derivatives was discussed.

Cytochrome P-450 Enzyme System↗
PubMed1987

Further studies on the persistence of neonatal androgen imprinting on sex-specific cytochrome P-450, testosterone and drug oxidations.

Neonatal castration completely suppressed the expression of P-450-male and expressed P-450-female; and testosterone treatment in a neonatal period partially reversed the effect of castration, i.e., neonatal imprinting (Kamataki et al., 1984; Waxman et al., 1985). In the present communication, we investigate the reversibility and persistency of neonatal imprinting on the expression of P-450-male and P-450-female. To our surprise, testosterone treatment at adulthood (8 weeks old) caused full expression of P-450-male and restored the activities of 2 alpha- and 16 alpha-testosterone hydroxylases in neonatally castrated rats. The levels of ethylmorphine N-demethylation, propoxycoumarin O-depropylation and benzo(a)pyrene hydroxylation were increased to the levels of adult male rats by adult testosterone-treatment. Moreover, treatment with testosterone of neonatally castrated rats at the age of 19 weeks did not cause a complete recovery of P-450-male content and drug-metabolizing activities. Testosterone administration into neonatal female rats did not significantly alter the contents of sex-dependent cytochrome P-450 and drug and steroid metabolizing activities in adulthood. Additional testosterone treatment in adulthood only slightly affected these parameters. All these results indicate that neonatal androgen imprinting on sex-dependent cytochrome P-450 and drug and steroid metabolizing activities in rat liver microsomes is not a permanent programming process and is modified by the presence and absence of sex-steroid hormones.

Androgens↗
PubMed1987

Human serum thyroglobulin determination with monoclonal antibody one-step assay: minimum interference of autoantibody.

Combination of two thyroglobulin monoclonal antibodies (monoAbs) recognizing epitopes which are rarely recognized by an antibody enabled us to develop a rapid one-step enzyme immunoassay of serum Tg. Of 87 monoclonal antibodies, 20 were selected for the purpose. The method is a sandwich technique employing a monoAb covering microplate and horse-radish peroxidase monoAb conjugate. A combination of monoAb 7A7A solid phase and 31A2E for the conjugate gave the best results. The assay takes 60 min and the minimal detectable amount is 2 ng/ml. Intraassay variation is from 4 to 7%. Interassay variation is 5 to 12%. The recovery rate for Tg added to normal sera is between 89 and 111%. The correlation coefficient with the polyclonal antibody method in Tg hemagglutination negative sera is 0.98. The presence of autoantibody in sera up to 10 X 2(4) hemagglutination titer does not affect the recovery rate to a statistically significant extent.

Antibodies, Monoclonal↗
PubMed1987

Alpha 1-adrenoceptor production of inositol phosphates mediates the inhibition of thyroxine release from the mouse thyroid.

To examine the mechanism of the alpha 1-adrenoceptor-mediated inhibition of the release of thyroid hormones in the mouse thyroid, the effect of noradrenaline on the production of inositol phosphates was investigated using thyroids preloaded with [3H]inositol. Noradrenaline increased [3H]inositol accumulation into inositol phosphates in the mouse thyroid during a 30-min incubation whereas TSH (10 mU/ml) was without effect. The effect of noradrenaline was mimicked by phenylephrine, but not by clonidine or isoprenaline. Prazosin antagonized the effect of noradrenaline, while yohimbine had no effect. These results suggest that noradrenaline-induced production of inositol phosphates is mediated by alpha 1-adrenoceptors. The inhibition of release of thyroid hormones elicited by alpha 1-adrenergic agonists in the mouse thyroid is possibly mediated through the hydrolysis of membrane phosphoinositides followed by the generation of second messengers such as inositol phosphates and diacylglycerol.

Animals↗
PubMed1987

Regulation of hepatic sulfotransferase catalyzing the activation of N-hydroxyarylamide and N-hydroxyarylamine by growth hormone.

The regulatory mechanism of hepatic sulfation of N-hydroxyarylamine and N-hydroxyarylamide by endocrine factors has been studied in rats. The cytosolic sulfations of N-hydroxy-2-acetylaminofluorene (N-hydroxy-AAF) and 2-hydroxyamino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (N-hydroxy-Glu-P-1), which were determined by the reductive formations of 2-acetylaminofluorene and Glu-P-1, were seven to nine times and three times higher, respectively, in male than female rats. Hypophysectomy of male rats decreased their activities to 23% and 41% of the levels of the untreated animals, respectively. Intermittent treatment of hypophysectomized male and female rats with human growth hormone (hGH) significantly increased their sulfating activities of both compounds. Infusion of hGH also enhanced the sulfating activity of N-hydroxy-AAF but not of N-hydroxy-Glu-P-1. The sulfating activity of N-hydroxy-AAF was also decreased by castration at neonate and was increased by the administration of testosterone propionate to gonadectomized male and female rats. Testosterone propionate and estradiol benzoate had no effect on hypophysectomized rats, but estradiol benzoate repressed the sulfating activities of N-hydroxy-AAF and N-hydroxy-Glu-P-1 in hGH-treated hypophysectomized male rats. These results indicate that sex steroids elicit their effects on the sulfations of N-hydroxyl-aryl compounds through modulating the action of growth hormone at hypothalamus-pituitary and hepatic levels in rat livers.

2-Acetylaminofluorene↗