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K Morohashi

Publications and source records attributed to K Morohashi.

77 records · Page 5Linked to original sources
PubMed1984

Induction of mRNA coding for phenobarbital-inducible form of microsomal cytochrome P-450 in rat liver by administration of 1,1-Di(p-chlorophenyl)-2,2-dichloroethylene and phenobarbital.

In the preceding paper (Yoshioka, H., et al. (1984) J. Biochem. 95, 937-947), we reported that 1,1-di(p-chlorophenyl)-2,2-dichloro-ethylene (DDE) induced the phenobarbital (PB)-inducible form of microsomal cytochrome P-450 (P-450(PB-1) in rat liver. In order to study more precisely the molecular events responsible for the induction of this particular form of cytochrome P-450 by the two chemical compounds, we determined the amounts of the mRNA coding for P-450(PB-1) in the liver of rats given a single dose of PB or DDE. RNA was extracted from the livers of the treated rats and the determination of the specific mRNA was carried out by using the rabbit reticulocyte lysate translation system and by a dot hybridization method using cloned P-450(PB-1) cDNA (Fujii-Kuriyama, Y., et al. (1982) Proc. Natl. Acad. Sci. U.S. 79, 2793-2797) as the probe. The amounts of P-450(PB-1) mRNA determined by these two methods at various time points of the induction process showed good agreement. These observations further confirmed the induction of an identical form of cytochrome P-450 by DDE and PB. The maximum level of P-450(PB-1) mRNA, which was about 8-fold higher than the control level, was attained at 20-30 h and at 48-72 h after the administration of PB and DDE, respectively. The mRNA level showed a rapid decrease after the peak in the liver of PB-treated rats, but the decrease was much slower with DDE-treated rats. We conclude that DDE had a more persistent inducing effect on the mRNA level than PB, although these two compounds induced an identical form of cytochrome P-450 in the liver microsomes of the animals.

Animals↗
PubMed1983

Position specificity in n-hexane hydroxylation by two forms of cytochrome P-450 in rat liver microsomes.

The hydroxylation of n-hexane by rat liver microsomes was studied and the contribution of different molecular species of cytochrome P-450 to the hydroxylation reaction was examined. In the case of untreated rats, the products of NADPH-dependent n-hexane hydroxylation were 1-, 2-, and 3-hexanols, and the major one was 2-hexanol. Phenobarbital (PB) treatment of animals resulted in a significant increase of the hydroxylation activity. The formation of 2- and 3-hexanols was much more significantly increased than that of 1-hexanol. On the other hand, 3-methylcholanthrene (MC) treatment stimulated the formation of 3-hexanol and the formation of the other two isomeric alcohols was rather decreased. These observations suggested the position specificities of the PB-inducible form (P-450(PB)) and MC-inducible form (P-450(MC)) of cytochrome P-450 in the hydroxylation of n-hexane. Inhibition experiments using antibodies specific to P-450(PB) and P-450(MC) also indicated that P-450(PB) was more active in the hydroxylation at the 2-position whereas P-450(MC) was more specific for the 3-position. NADPH-dependent n-hexane hydroxylation systems were reconstituted by the use of purified NADPH-cytochrome P-450 reductase and P-450(PB) or P-450(MC), and the activities of the reconstituted systems supported the proposed position specificities of these two forms of cytochrome P-450 in n-hexane hydroxylation.

Animals↗
PubMedDate not supplied

Expression profiles of COUP-TF, DAX-1, and SF-1 in the human adrenal gland and adrenocortical tumors: possible implications in steroidogenesis.

Chicken ovalbumin upstream promoter-transcription factor (COUP-TF), DAX-1, and steroidogenic factor-1 (SF-1) are orphan members of the nuclear hormone receptor superfamily. COUP-TF and DAX-1 have been shown to negatively regulate the transcriptional activity of SF-1, a steroidogenic cell-specific activator of various steroidogenic cytochrome P450 genes. We therefore examined the expression levels and immunolocalization of COUP-TF, DAX-1, and SF-1 in human adrenal gland (NL) and adrenocortical adenomas, and compared the results with CYP17 expression levels and its enzyme activities to study their potential correlation with adrenocortical steroidogenesis. In NL (n = 10), expressions of COUP-TF, DAX-1, and SF-1 were detected in the nuclei of adrenocortical cells, but not in the medulla. In cortisol-producing adenomas causing Cushing syndrome (CS, n = 20), CYP17 expression was upregulated (298 +/- 2% vs NL 98 +/- 4%), whereas expression levels of both COUP-TFs (COUP-TFI, 52 +/- 5% vs NL 98 +/- 4%; COUP-TFII, 18 +/- 4% vs NL 98 +/- 4%) and DAX-1 (42 +/- 4% vs NL 100 +/- 4%) were reduced. In deoxycorticosterone-producing adenomas (DOC, n = 2), on the other hand, CYP17 expression was extremely reduced (8 and 12% vs NL 98 +/- 4%), whereas DAX-1 expression increased markedly (350 and 360% vs NL 100 +/- 4%). Expression levels of SF-1 did not differ between NL (100 +/- 8%) and CS (106 +/- 10%), but its expression appeared to be decreased in DOC (25 and 20%). These results showed CYP17 expression to be upregulated and downregulated in CS and DOC, respectively, in a manner reciprocal to that of its repressors, COUP-TF and/or DAX-1. In summary, the results indicate that co-localization of COUP-TF, DAX-1, and SF-1 in NL was lost in adrenocortical tumors and that these orphan receptors play an important role in the regulation of steroidogenesis in human adrenals.

Adenoma↗