Journal ArticleDOI
Effects of different steroid-biosynthesis inhibitors on the testicular steroidogenesis of the toad Bufo arenarum.
L F Canosa,N R Ceballos +1 more
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Testis fragments from Bufo arenarum were incubated with different steroid-biosynthesis inhibitors and cyanoketone (CNK), spironolactone (SPNL) and finasteride (FIN) to determine the degree of inhibition exerted by the inhibitors used.Abstract:
Testis fragments from Bufo arenarum were incubated with [7(n)-3H]pregnenolone (P5), [1,2-3H]dehydroepiandrosterone (DHEA) and [1,2,6,7-3H]testosterone (T), and different steroid-biosynthesis inhibitors. The inhibitors used were: cyanoketone (CNK), spironolactone (SPNL) and finasteride (FIN). CNK significantly increased the recovery of 3β-hydroxy-5-ene steroids while SPNL reduced the metabolism of P5 and the production of C19-steroids. The metabolism of C19-substrates was only modified by CNK, which reduced the transformation of DHEA without modifying the metabolism of T. To determine the degree of inhibition exerted by the inhibitors used, the activities of the enzymes were estimated as the percentage of their contribution to the total steroid metabolism. CNK strongly inhibited the activity of hydroxysteroid dehydrogenase/isomerase if its contribution was estimated using both P5 and DHEA. If the analysis was made considering both activities associated to cytochrome P450 17α-hydroxylase, C17–20 lyase (P450c17), it became evident that SPNL inhibited both of them. The percent contribution of 17β-hydroxysteroid dehydrogenase (17βHSD) activity diminished in the presence of CNK only if it was estimated considering P5 and DHEA metabolism. SPNL produced a significant inhibition of 17βHSD when its contribution was estimated considering P5 metabolism. However, SPNL was insufficient if DHEA or T were considered. The effect of SPNL on the contribution of 17βHSD could be due to the reduction of C19-substrates. The activity of 5α-reductase was inhibited by CNK only if results from P5 and DHEA were considered.read more
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Journal ArticleDOI
The OECD validation program of the H295R steroidogenesis assay: Phase 3. Final inter-laboratory validation study
Markus Hecker,Henner Hollert,Ralph L. Cooper,Anne Marie Vinggaard,Yumi Akahori,Margaret B. Murphy,Christine Nellemann,Eric Higley,John L. Newsted,John W. Laskey,Angela R. Buckalew,Stefanie Grund,Sibylle Maletz,John P. Giesy,Gary Timm +14 more
TL;DR: In the original article wrong unites were quoted in Table 3 (page 508) and Table 4 (page 510) as well as in the paragraph 3.2 Core chemical exposure experiments on page 509 as mentioned in this paper.
The OECD validation program of the H295R steroidogenesis assay. Phase 3: Final Inter-Laboratory Validation Study. Environ Sci Pol Res
Markus Hecker,Henner Hollert,Ralph L. Cooper,Anne Marie Vinggaard,Yumi Akahori,Margaret B. Murphy,Christine Nellemann,Eric Higley,John Newsted,John W. Laskey,Angela R. Buckalew,Stefanie Grund,Sibylle Maletz,John P. Giesy,Gary Timm +14 more
TL;DR: The H295R steroidogenesis assay protocol successfully identified the majority of chemicals with known and unknown modes of interaction as inducers or inhibitors of T and E2 production, and can be considered a reliable screen for chemicals that can alter the production of sex steroid hormones.
Journal ArticleDOI
Elevated expression of P450c17 (CYP17) during testicular formation in the frog.
TL;DR: CYP17 expression was much higher in male gonads than in female ones during sex determination in R. rugosa, and in situ hybridization analysis revealed that CYP17 was expressed in somatic cells of the indifferent male gonad and in those of the testis.
Journal ArticleDOI
Immunohistochemical detection and biological activities of CYP17 (P450c17) in the indifferent gonad of the frog Rana rugosa.
Nana Sakurai,Koichi Maruo,Shogo Haraguchi,Yoshinobu Uno,Yuki Oshima,Kazuyoshi Tsutsui,Yoichi Matsuda,Jean Luc Do Rego,Georges Pelletier,Hubert Vaudry,Masahisa Nakamura +10 more
TL;DR: The results demonstrate that the CYP17 protein is synthesized in somatic cells of the indifferent gonad during gonadal sex differentiation in R. rugosa and that it is more active in converting Prog to AE in males than in females.
Journal ArticleDOI
Seasonal changes in testicular steroidogenesis in the toad Bufo arenarum H.
TL;DR: In amphibians, Bufo arenarum showed that during the reproductive season, the production of progesterone, 5alpha-pregnan-3alpha,20alpha-diol, 3alpha-hydroxy-5alpha-propnan-20-one, and 5-androstane-3beta,17beta,diol as intermediate in testosterone biosynthesis increases significantly as mentioned in this paper.