Showing results 101 to 112 of 112
  Ontogenic development of steroid 16 alpha-hydroxylase as a tool for the study of the multiplicity of cytochrome P-450.Pasleau, Françoise  ; ; Kremers, Pierre et alin European Journal of Biochemistry (1981), 120 1. Activities of progesterone, testosterone, pregnenolone and dehydroepiandrosterone 16 alpha-hydroxylase are undetectable in the fetal rat liver. During the neonatal period, the four enzymic activities ... [more ▼] 1. Activities of progesterone, testosterone, pregnenolone and dehydroepiandrosterone 16 alpha-hydroxylase are undetectable in the fetal rat liver. During the neonatal period, the four enzymic activities increase in parallel to the concentration of cytochrome P-450. Until puberty, they develop similarly in male and female rat livers. From the 40th to the 55th day, the four steroid 16 alpha-hydroxylase activities increase rapidly in the male rat liver. The sexual differentiation of the steroid 16 alpha-hydroxylation observed in adult male and female rats takes place around the 55th day. 2. In the adult rat liver, steroid 16 alpha-hydroxylase is supported by two forms of cytochrome P-450 (form I and form II), which differ in their relative affinities for the various steroid substrates, and by their relative proportions in male and female rat livers. These two forms of cytochrome P-450 are also present in the young male and female rat livers, but are roughly equal in proportion. The transition from the immature to the adult repartition of the two forms occurs during puberty and is correlated with the sexual differentiation of the steroid 16 alpha-hydroxylase activities. 3. During the critical phases of the rat ontogenic development, the in vitro interactions between benzo[a]pyrene and steroids were compared at the level of two rat liver monooxygenases: steroid 16 alpha-hydroxylase and aryl hydrocarbon hydroxylase. (a) In the immature male and female rat livers, progesterone 16 alpha-hydroxylase, and to a lesser extent, pregnenolone 16 alpha-hydroxylase are inhibited by benzo[a]pyrene. Progesterone 16 alpha-hydroxylase is also inhibited by metyrapone. (b) In the young rat, aryl hydrocarbon hydroxylase cannot be inhibited by steroids and appears to be supported by a single form of cytochrome P-450. The transition from the immature to the adult situation occurs around the 40th day. [less ▲] Detailed reference viewed: 14 (2 ULg)Competition between benzo[a]pyrene and various steroids for cytochrome P-450-dependent rat liver monooxygenases.Pasleau, Françoise ; Kremers, Pierre ; in Chemico-Biological Interactions (1981), 34 Cytochrome P-450-dependent monooxygenases are able to oxidize a large variety of endogenous and exogenous substrates. This paper describes the in vitro interaction between benzopyrene and steroids at the ... [more ▼] Cytochrome P-450-dependent monooxygenases are able to oxidize a large variety of endogenous and exogenous substrates. This paper describes the in vitro interaction between benzopyrene and steroids at the level of two rat liver monooxygenases: steroid-16 alpha-hydroxylase and aryl hydrocarbon hydroxylase (AHH). The results obtained suggest the following conclusions: (1) Steroid-16 alpha-hydroxylase is partially supported by a specific cytochrome P-450 form which is not inhibited in vitro by exogenous substrates. Steroid-16 alpha-hydroxylase is completely independent from cytochrome P1-450 (or P-448), as it is insensitive, in vitro, to alpha-naphthoflavone; (2) AHH is supported by two cytochrome P-450 forms: a specific form which is inducible by methylcholanthrene and inhibited in vitro by alpha-naphthoflavone, but is insensitive to metyrapone and steroids; and another less specific form which is inhibited by metyrapone and steroids in vitro. [less ▲] Detailed reference viewed: 5 (0 ULg) Différenciation sexuelle et interaction avec des substrats exogène des 16alpha-hydroxylases de stéroïdes au cours de leur développement ontogénique.Pasleau, Françoise ; ; Poster (1980, October 18) Detailed reference viewed: 6 (0 ULg)Sex differences in the activity of different cytochrome P450 dependent steroid 16alpha-hydroxylases in rat liverPasleau, Françoise ; Kremers, Pierre ; in Journal of Steroid Biochemistry & Molecular Biology (1980), 13 Detailed reference viewed: 24 (0 ULg)Biochemical and biological properties of steroid 16alpha-hydroxylase.; ; et al Conference (1980, March) Detailed reference viewed: 6 (0 ULg)Steroid 16alpha-hydroxylase multiplicity in rat liver.; Kremers, Pierre ; Pasleau, Françoise in Biochemistry, Biophysics and Regulation of Cytochrome. (1980) Detailed reference viewed: 9 (1 ULg)Ontegenesis of steroid 16alpha-hydroxylase multiple forms in the rat liver : development of the sexual differenciation and interactions with exogenous lipophilic compounds.Pasleau, Françoise ; ; et alPoster (1980) Detailed reference viewed: 10 (0 ULg)Régulation de l’activité des monooxygénases microsomales au cours de la croissance.; Kremers, Pierre ; Pasleau, Françoise in Les Colloques de l'INSERM, Pharmacologie du Développement (1979) Detailed reference viewed: 12 (0 ULg)Influence possible des facteurs nutritionnels sur l'ontogenèse de certaines formes de cytochrome P450.Pasleau, Françoise ; Kremers, Pierre ; Conference (1978, December) Detailed reference viewed: 10 (2 ULg)Is steroid 16alpha-hydroxylase supported by more than one mono-oxygenase.Kremers, Pierre ; Pasleau, Françoise ; in Biochemical and Biophysical Research Communications (1978) Steroid-16α-hydroxylase activities have been measured in normal and induced rat livers using four different substrates. The male/female activity ratio as well as the induction factor vary with the ... [more ▼] Steroid-16α-hydroxylase activities have been measured in normal and induced rat livers using four different substrates. The male/female activity ratio as well as the induction factor vary with the substrate indicating that steroid-16α-hydroxylase activity is a heterogenous enzyme. Experiments using specific inhibitors led to the conclusion that steroid-16α-hydroxylase is supported by at least two cytochrome P-450 forms, different from the cytochrome P-448. [less ▲] Detailed reference viewed: 15 (6 ULg)Multiplicity of cytochrome P450 dependent steroid 16alpha-hydroxylase in the rat liver.Kremers, Pierre ; Pasleau, Françoise ; Conference (1978, June) Detailed reference viewed: 12 (3 ULg)Recherches sur la position phylétique des Téléostéens gonorhynchiformes, basées sur l'étude de l'ostéologie et de la myologie céphaliquePasleau, Françoise Master's dissertation (1974) Detailed reference viewed: 6 (1 ULg) |
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