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H Takikawa

Publications and source records attributed to H Takikawa.

At least 91 records · Page 5Linked to original sources
PubMed1991

Glucuronidation of bile acids by their high-dose infusion into rats.

We previously reported that high-dose infusion of ursodeoxycholate into rats caused its extensive glucuronidation. In this study, the glucuronidation of various bile acids after high-dose infusion into rats was examined and the effects of coinfusion of bile acids on the glucuronidation of a trace dose of [14C]deoxycholate were also studied. Sixty minutes after infusion of 14C-bile acids at a rate of 1 mumol/min/100 gm, the glucuronidation of the labeled bile acid in the bile was 31%, 15%, 8% and 3% for deoxycholate, ursodeoxycholate, chenodeoxycholate and cholate, respectively. The infusion of a trace dose of [14C] deoxycholate resulted in only 2% glucuronidation, and coinfusion of taurochenodeoxycholate or tauroursodeoxycholate at a rate of 1 mumol/min/100 gm did not change the percentage of glucuronidation of [14C]deoxycholate. However, coinfusion of chenodeoxycholate, ursodeoxycholate or cholate at the same rate markedly increased the percentage of the [14C]deoxycholate-glycuronide in the bile (35%, 18% and 36%, respectively). Thus glucuronidation of bile acids by high-dose infusion into rats occurs predominantly with deoxycholate and is not specific for ursodeoxycholate, and glucuronidation depends on the unconjugated bile acid load, which might be regulated by the capacity of amidation by the liver.

Animals↗
PubMed1990

Oxidation and reduction of bile acid precursors by rat hepatic 3 alpha-hydroxysteroid dehydrogenase and inhibition by bile acids and indomethacin.

Enzyme kinetics of purified rat hepatic 3 alpha-hydroxysteroid dehydrogenase for bile acid precursors and effects of bile acids and indomethacin on those activities were studied. This enzyme catalyzed the oxidoreduction of the C3 position of bile acid precursors. Km for 7 alpha, 12 alpha-dihydroxy-5 beta-cholestan-3-one (1.6 microM) was markedly lower than Km for 7 alpha-hydroxy-5 beta-cholestan-3-one (28 microM) but Vmax was similar. Km for 3 alpha, 7 alpha-dihydroxy-5 beta-cholestane (12 microM) was lower than Km for 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestane (150 microM) although Vmax/Km values were similar for both compounds. Bile acids and indomethacin inhibited the reduction of 3-oxo bile acid precursors. NADPH inhibited the binding of lithocholic acid (3 alpha-hydroxy-5 beta-cholanic acid) by 3 alpha-hydroxysteroid dehydrogenase. These data suggest that intrahepatic bile acid concentrations may affect the reduction of 3-oxo-bile acid precursors and intrahepatic redox conditions may affect intracellular bile acid transfer.

3-Hydroxysteroid Dehydrogenases↗
PubMed1990

Relationship between the newly identified bile acid binder and bile acid oxidoreductases in human liver.

Gel filtration fractions of human hepatic cytosol obtained from an autopsy liver were examined for elution of bile acid oxidoreductases. Several enzymes including 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD), 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), 3-ketosteroid reductase, and dihydrodiol dehydrogenase eluted mainly in the 30,000-40,000 Mr fractions known to contain the newly identified bile acid binder (Stolz, A., Sugiyama, Y., Kuhlenkamp, J., and Kaplowitz, N. (1984) FEBS Lett. 177, 31-35). These enzyme activities could be resolved into six peaks of dihydrodiol dehydrogenase activity on chromatofocusing, some of which also had oxidoreductase activity with bile acids. Using equilibrium dialysis, the major lithocholate-binding activity was found to coelute with 3 beta-HSD, completely separate from 3 alpha-HSD. Reexamination of the surgical liver specimen originally used to purify the bile acid binder confirmed these results. The peak fraction from chromatofocusing, which exhibited the bulk of binding activity with bile acids, had 3 beta-HSD activity, whereas other fractions had 3 alpha-HSD. Anti-serum to the previously purified binder identified a single 36-kDa protein in both liver specimens and exclusively in the chromatofocusing fractions containing both the binding and 3 beta-HSD activity. However, upon further purification of the binder from this fraction, 3 beta-HSD activity was separated from the binder, but the homogeneous protein retained dihydrodiol dehydrogenase activity. Thus, in contrast to the rat in which the major bile acid binder is identical to 3 alpha-HSD, in human liver the bile acid binder is distinct from 3 alpha-HSD and copurifies with a different oxidoreductase that has dihydrodiol dehydrogenase activity but no activity with bile acids.

3-Hydroxysteroid Dehydrogenases↗
PubMed1990

The ursodeoxycholate dose-dependent formation of ursodeoxycholate-glucuronide in the rat and the choleretic potencies.

The reason for the discrepancy between bile flow and biliary bile acid excretion during ursodeoxycholate infusion in rats is unknown. We found that ursodeoxycholate-glucuronide is formed during ursodeoxycholate infusion at higher doses. Ursodeoxycholate infusion (1 to 3 mumol/min/100 gm body weight) for 90 min caused marked hypercholeresis, and the previously reported discrepancy between bile flow and biliary bile acid excretion was observed when bile acid concentrations were measured by regular enzymatic methods. However, the appearance of ursodeoxycholate-glucuronide was observed on thin-layer chromatography analysis and up to 30% of the ursodeoxycholate in bile was found to be glucuronidated when determined by the enzymatic method after beta-glucuronidase treatment. The choleretic activity of ursodeoxycholate-glucuronide (25.2 microliters/mumol) was about 3 times higher than that of ursodeoxycholate (8.9 microliters/mumol) when infused at 0.25 mumol/min/100 gm body weight and ursodeoxycholate-glucuronide also stimulated higher biliary bicarbonate excretion than ursodeoxycholate. These results indicate that the discrepancy between bile flow and biliary bile acid excretion caused by high-dose infusion of ursodeoxycholate into rats can be explained by glucuronide conjugation of ursodeoxycholate that cannot be detected by the regular enzymatic method. The glucuronidation of ursodeoxycholate might also be important in the ursodeoxycholate-induced increase in biliary bicarbonate excretion.

Animals↗
PubMed1990

Effects of OK-432 (Picibanil) on estrogen receptor levels and tamoxifen treatment in 7,12-dimethylbenz[a]anthracene-induced rat mammary cancers.

The effects of OK-432 (Picibanil) on estrogen receptor (ER) levels and subsequent tamoxifen (TAM) treatment were examined in 189 female Sprague-Dawley rats with 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary cancers. When OK-432 was administered (0.1 KE/kg i.p. once weekly) for 12 weeks to the rats after DMBA, the average ER level of the TAM-responsive tumors in the OK-432-treated group was significantly higher than that in the control group. The antitumor effect of TAM was significantly greater in the OK-432-treated group. When OK-432 was administered to rats with established DMBA tumors, the average ER levels did not change significantly after 2 or 4 weeks of treatment. ER levels in the control group (no treatment) fell significantly after 2 or 4 weeks. These results suggest that hormone dependence of DMBA-induced rat mammary cancers may be maintained or augmented by the administration of OK-432.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1990

Acute decrease in vitellogenin synthesis by deprivation of food and water in laying hens.

Vitellogenin synthesis during a decrease in egg production caused by depriving food and water was investigated in Single Comb White Leghorn hens. They were transferred from long days of 14L: 10D to short days of 10L: 14D 5 days before food and water deprivation. Then food was deprived for 5 days and water for 2 days. The body weight was markedly decreased by the treatment and reached its minimum after 5 days. The egg production rate which was 85% before the treatment was nil after 4 days. On day 3 the circulating vitellogenin concentrations, measured by a newly established RIA system, was markedly decreased by deprivation of food and water to 22% of the pretreatment level. The concentrations remained less than 10% during cessation of egg laying. Serum luteinizing hormone (LH) and progesterone concentrations decreased gradually, but estradiol 17 beta (E2) decreased abruptly. This acute decrease closely coincided with the decrease in egg production and the weight of the oviduct and ovary. These concentrations were gradually increased after day 16 and returned to the normal level after 46 days. Circulating thyroxine (T4) and triiodothyronine (T3) concentrations gradually increased from the beginning of the change in the day length and peaked on day 7 or 9, whereas reverse (r)T3 rapidly increased. The concentrations again decreased at the beginning of molting which occurred later due to the deprivation of food and water. Thus, these results demonstrated for the first time that the decrease in egg production induced by deprivation of food and water closely related to the decrease in vitellogenin synthesis as well as gonadal and pituitary functions. Further, recovery of egg production was coupled with the increase in the ovary and oviduct weight, and circulating LH, E2, progesterone, and vitellogenin.

Animals↗
PubMed1990

The gene for the beta subunit of porcine FSH: absence of consensus oestrogen-responsive element and presence of retroposons.

To elucidate the structure and control of expression of the porcine FSH-beta subunit gene, two genomic clones were isolated and the entire gene structure was determined to the extent of 10 kb, consisting of 6 kb of the 5'-flanking region and 4 kb of the transcriptional unit. The porcine FSH-beta gene consisted of three exons the same as the human and bovine genes, but the positions of both splicing sites of porcine intron-1 were unique. It is known that the synthesis of FSH is regulated by gonadal steroids, gonadotrophin-releasing hormone (GnRH) and inhibin. However, the consensus steroid-responsive element was unexpectedly absent in the 5'-flanking region of 6 kb. On the other hand, the potential binding sites for activator protein-1 (AP1) and AP2, which might be stimulated by the GnRH-protein kinase C cascade, were present at seven and five positions respectively. An imperfect cyclic AMP-responsive element was also present. Southern blot analyses, using the cDNA and genomic fragments as probes, gave smear patterns suggesting the presence of repetitive sequences in the porcine FSH-beta gene. A survey of homology with the repetitive sequences revealed that short interspersed repeated sequences (SINES)-type non-viral retroposons were present with about 250 bp length repeats twice in the 5'-flanking region and once each in intron-1 and the 3'-flanking region. Other SINES-like sequences were also found in intron-1, exon-2 and exon-3. In comparison with the 5'-flanking sequences of the porcine alpha and LH-beta genes, there were no significantly conserved regions, implying a lack of common modulation of the three subunit genes.

Amino Acid Sequence↗
PubMed1990

Effects of sequential and combined endocrine therapies on the growth of 7,12-dimethylbenz [alpha] anthracene-induced rat mammary carcinoma.

Sixty-six female Sprague-Dawley (SD) rats with 7,12-dimethylbenz [alpha] anthracene(DMBA)-induced rat mammary cancer were divided into five groups: tamoxifen (TAM), medroxyprogesterone acetate (MPA), TAM + MPA, ovariectomy (Ovex), control (no treatment). An antitumor effect was shown in each treated group. Thirty-six (72%) out of 50 treated animals responded to the first endocrine therapy. Moreover, tumors disappeared completely from 21 out of the 36 animals, and no new tumors were seen until the 12th week. The facts suggest experimental hormone, when compared to clinical, therapy in DMBA-induced tumors to have a higher response rate. A total of 14 out of 50 tumors failed to respond to the first treatment (resistant tumor). There was no significant difference in the proportion of resistant tumors among the four treated groups. When other endocrine therapies were tried out of resistant tumors, seven out of the 14 responded, the resistant tumors in the TAM group responding significantly well to the other endocrine therapies compared to those in the MPA group (P less than 0.05). These results suggest the possibility of resistant tumors responding to different types of endocrine therapy.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Purification and characterization of 55-kDa protein with 3,5,3'-triiodo-L-thyronine-binding activity and protein disulfide-isomerase activity from beef liver membrane.

Beef liver membranes were shown to have different kinds of 3,5,3'-triiodo-L-thyronine binding proteins including the 55-kDa protein which had been reported to have this activity in many cells by affinity labelling with N-bromoacetyl-3,5,3'-[125I]triiodo-L-thyronine. In order to characterize the molecular features of these binding proteins, the 55-kDa protein was purified from a beef liver membrane fraction abundant in the plasma membrane. The protein was solubilized with 0.5% Chaps and purified by chromatography on gel filtration, hydroxyapatite, and Mono Q anion-exchange columns. The purity was confirmed with reversed-phase HPLC and SDS/PAGE. Consequently, 0.4% of the total proteins in the membrane fraction was recovered as the 55-kDa protein. One fourth of the amino acid composition of this protein was Glx (14.6%) plus Asx (11.7%) and the pI of this protein was 4.5. The purified protein has triiodothyronine-binding activity with a Kd of 57 nM which is similar to the high-affinity binding site of the membranes. The anti-(55-kDa protein) sera specifically recognized the 55-kDa protein of beef, rat and human cells. The immunoglobulin G fraction of the anti-(55-kDa protein) sera inhibited triiodothyronine binding to the beef liver membrane fraction. The purified protein also showed the activity of protein disulfide-isomerase (EC 5.3.4.1) as determined by reactivating scrambled ribonuclease. These data strongly suggested that the multi-functional 55-kDa protein which has triiodothyronine-binding activity and the activity of protein disulfide-isomerase, which is also reported to be the beta subunit of prolyl-4-hydroxylase, glycosylation-site-binding protein of oligosaccharyl transferase and iodothyronine 5'-monodeionidase, could be significant in the action of triiodothyronine towards the target cells.

Amino Acids↗
PubMed1989

Comparison of biliary excretion and metabolism of lithocholic acid and its sulfate and glucuronide conjugates in rats.

Biliary excretion and biotransformation of tracer doses of [14C]lithocholic acid and its sulfate and glucuronide intravenously injected into bile-drainaged rats were compared. Biliary excretion efficiency was in the order of unconjugate sulfate glucuronide and all conjugates were completely excreted into bile within 60 min after injection. Only tracer doses of radioactivity were found in the liver and urine. About 90% of radiolabeled bile acids in bile were conjugated with taurine immediately after injection of lithocholic acid, whereas lithocholic acid-glucuronide was only partly conjugated with taurine all the time (less than 6%) and excreted into bile mainly as native compound. In the first 10 min, 66% of lithocholic acid-sulfate was conjugated with taurine and it gradually proceeded up to 87%. Hydroxylation at C-6 and C-7 positions of lithocholic acid proceeded time-dependently up to 45%. No hydroxylation was observed with lithocholic acid-sulfate or glucuronide. Differences of biliary excretion rate of these conjugates may be one of the reasons for the delayed decrease of sulfated and glucuronidated bile acids in serum after bile drainage to patients with obstructive jaundice of during the recovery of acute hepatitis than non-esterified bile acids.

Animals↗
PubMed1989

Molecular cloning of cDNAs for precursors of porcine pituitary glycoprotein hormone common alpha-subunit and of thyroid stimulating hormone beta-subunit.

cDNA clones encoding precursors of glycoprotein hormone common alpha-subunit (pre-alpha) and of thyroid stimulating hormone beta-subunit (pre-TSH beta) were isolated from a porcine anterior pituitary cDNA library using DNA probes, and the nucleotide sequences were determined. The nucleotide sequence of pre-alpha cDNA contained an entire coding region (360 bases) including 5' and 3' untranslated regions. The pre-alpha mRNA was about 900 bases long. The predicted amino acid sequence consisted of a signal peptide of 24 amino acid residues and a mature alpha-subunit protein of 96 residues. Six amino acid residues at the amino terminus of the predicted mature protein had not been found by direct amino acid sequencing of the purified protein. The nucleotide sequence of pre-TSH beta cDNA contained an entire coding region and a 3' untranslated region which has two polyadenylation signals. The length of the pre-TSH beta mRNA was about 500 bases long. The predicted amino acid sequence consisted of a signal peptide of 20 amino acid residues, a mature protein of 112 residues and an additional extension of six amino acid residues at the carboxyl terminus, which had not been found in the amino acid sequence of the purified protein. The coding sequences of the cDNAs showed high homologies with those of other mammalian species (84-93% for pre-alpha and 81-94% for pre-TSH beta). Comprehensive data of our serial molecular cloning for porcine glycoprotein hormones revealed low but significant homologies (34-40%) among three beta-subunits. Upon comparison of frequency of (U)n A sequence in 3' untranslated region, porcine pre-alpha and pre-TSH beta mRNAs were grouped into a moderate class of mRNA stability whereas porcine pre-FSH beta and pre-LH beta were grouped into unstable and stable classes, respectively.

Amino Acid Sequence↗
PubMed1989

Effects of trilostane on 7,12-dimethylbenz[a]anthracene-induced rat mammary cancers and body weight of rats in relation to estrogen receptors.

Effects of trilostane (TLS) on 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary cancers and body weight of rats were examined in relation to estrogen receptors (ER) in 103 female Sprague-Dawley rats with DMBA-induced cancers. The inhibitory effects of the treated groups on the growth of DMBA-induced rat mammary cancers were significantly stronger than those of the control group at many points during the treatment, demonstrating a more remarkable inhibitory effect in the high-dose groups of 300 and 500 mg/kg. In the high-dose groups, the inhibitory effects of TLS tended to be slightly stronger in the ER-negative groups than in the ER-positive groups. These results suggest that the mechanisms of action of TLS are not influenced by the presence or absence of ER, but are due to complicated hormonal changes induced by the inhibition of steroid biosynthesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Uptake of 3,5,3'-L-tri-iodothyronine in human erythrocytes.

The mechanisms of 3,5,3'-L-tri-iodothyronine (T3) uptake into human erythrocytes were examined. Purified membranes of human erythrocytes were shown to have two classes of T3-binding sites with one being a high-affinity site (dissociation constant, 59.2 +/- 17.8 nmol/l; maximum binding capacity, 344.3 +/- 95.5 fmol/micrograms protein). Furthermore, it was shown that there were two pathways for T3 uptake in human erythrocytes; one was saturable, stereospecific (T3 much greater than thyroxine greater than 3,5,3'-D-tri-iodothyronine), energy-dependent and dominant at 15 degrees C; the other was not displaced by unlabelled T3 and was energy-independent but did not occur by passive diffusion. The former pathway which, it is suggested, is a receptor-mediated transport pathway, was inhibited by monodansylcadaverine, phloretin or oligomycin at 15 or 37 degrees C, but the latter pathway was not inhibited by these inhibitors. Our results strongly suggest that uptake of T3 by the energy-independent pathway became predominant over the energy-dependent pathway at 37 degrees C and accounted for 83% of total T3 uptake of human erythrocytes.

Binding, Competitive↗
PubMed1989

Sequential hormone therapy with medroxyprogesterone acetate for 7, 12-dimethylbenz [alpha] anthracene-induced rat mammary tumors.

Two types of sequential hormone therapy with medroxyprogesterone acetate (MPA) were examined in female 93 Sprague--Dawley (SD) rats with 7,12-dimethylbenz [alpha] anthracene (DMBA)-induced mammary tumors. Estradiol (E2) priming induced progesterone receptors (PgR) in most cases and, after induction of PgR, MPA often showed an augmented antitumor effect. For this reason, E2 priming + MPA had a more marked antitumor effect on DMBA tumors than MPA alone. Tamoxifen (TAM) (0.1 mg/kg) priming induced PgR more frequently than TAM (0.4 mg/kg) priming. Furthermore, treatment with TAM priming (0.1 mg/kg) + MPA showed a more marked antitumor effect than with TAM priming (0.4 mg/kg) + MPA or MPA alone. In the above two priming therapies with MPA, the latter is more practical for the clinical treatment of breast cancer than the former because the mechanism of action of E2 is usually thought to show tumorigenic activity on breast cancer, while the mechanism of action of TAM is thought to show an antitumor effect. It is suggested that the sequence of administration of MPA after TAM priming may be favorable for the treatment of breast cancer.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

Comparison of the effects of bile acids and GSH on the fluorescence of bound 1-anilino-8-naphthalene sulfonate and the enzymatic activity of cationic and neutral human hepatic GSH S-transferases.

Three cationic (C1, C2, A1) and a neutral (N1) glutathione (GSH) S-transferase were purified to homogeneity from human liver, as we have previously reported. GSH had no effect on the fluorescence of 1-anilino-8-naphthalene sulfonate (ANS) bound by transferase C1 and N1, but markedly enhanced the fluorescence with C2 and A1 without changing the affinity for ANS. This effect of GSH was saturable and with C2 was intermediate between A1 and C1. Bile acids inhibited the fluorescence of ANS bound to C1 and C2. GSH in the presence of bile acids further decreased the fluorescence of ANS bound to C1 and increased the fluorescence with C2. Transferase A1 showed decreased fluorescence in the presence of lithocholic acid and increased fluorescence in the presence of cholic acid; both changes were reversed by GSH. Transferase N1 showed increased fluorescence of bound ANS in the presence of various bile acids and this effect was diminished in the presence of GSH. Enzyme activity of the transferase was inhibited by bile acids with the exception of transferase A1. All the proteins bound lithocholic acid. The inhibition of C1 and N1 was greater at pH 6.5 than 7.4 and the order of addition of substrates and inhibitor made no difference.

Anilino Naphthalenesulfonates↗