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Titolo:
IN-VIVO BIOTRANSFORMATION OF TESTOSTERONE BY PHASE-I AND PHASE-II DETOXICATION ENZYMES AND THEIR MODULATION BY 20-HYDROXYECDYSONE IN DAPHNIA-MAGNA
Autore:
BALDWIN WS; LEBLANC GA;
Indirizzi:
N CAROLINA STATE UNIV,DEPT TOXICOL,BOX 7633 RALEIGH NC 27695 N CAROLINA STATE UNIV,DEPT TOXICOL,BOX 7633 RALEIGH NC 27695
Titolo Testata:
Aquatic toxicology
fascicolo: 1-2, volume: 29, anno: 1994,
pagine: 103 - 117
SICI:
0166-445X(1994)29:1-2<103:IBOTBP>2.0.ZU;2-S
Fonte:
ISI
Lingua:
ENG
Soggetto:
RAT HEPATIC CYTOCHROME-P-450; METABOLISM; STEROIDS; ISOZYMES; INVITRO; LIVER; REGIOSELECTIVITY; PURIFICATION; EXPRESSION; ECDYSONE;
Keywords:
TESTOSTERONE; DAPHNIA-MAGNA; OXIDATION; CONJUGATION; 20-HYDROXYECDYSONE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
32
Recensione:
Indirizzi per estratti:
Citazione:
W.S. Baldwin e G.A. Leblanc, "IN-VIVO BIOTRANSFORMATION OF TESTOSTERONE BY PHASE-I AND PHASE-II DETOXICATION ENZYMES AND THEIR MODULATION BY 20-HYDROXYECDYSONE IN DAPHNIA-MAGNA", Aquatic toxicology, 29(1-2), 1994, pp. 103-117

Abstract

Phase I and phase II chemical detoxication processes were elucidated in Daphnia magna using in vivo techniques and [C-14]testosterone as a substrate. Testosterone was used because this compound undergoes multiple biotransformations and its metabolites are well characterized in other species. In addition, regulation of these processes by the endogenous steroid hormone, 20-hydroxyecdysone, was investigated. Daphnids produced at least ten polar phase I metabolites and four nonpolar phaseI metabolites of testosterone. Six of the ten polar metabolites have been identified as monohydroxy-products of testosterone. The polar metabolites were preferentially excreted while the nonpolar metabolites were preferentially retained by the daphnids. In addition, testosteroneand all phase I metabolites were also excreted as glucose conjugates. A polar metabolite designated 'C' was preferentially conjugated with glucose over the other metabolites. Testosterone and its polar phase Imetabolites were also excreted as sulfate conjugates with 2alpha-hydroxytestosterone being the predominant sulfate-conjugated metabolite. In contrast to glucose conjugation, no nonpolar phase I metabolites of testosterone were sulfate conjugated. Twenty-four hour pre-exposure ofdaphnids to 4.2 muM 20-hydroxyecdysone did not affect phase I metabolism of testosterone, but differentially modulated phase 11 conjugationin a manner suggesting the presence of at least two glucosyltransferases and two sulfotransferases. Treatment with 20-hydroxyecdysone significantly increased the elimination of sulfate conjugates due largely to increased sulfate conjugation of unmetabolized testosterone. These results demonstrate that daphnids can convert polycyclic compounds to multiple polar and nonpolar metabolites resulting from both phase I andphase II biotransformations, and that some phase II activities are under the regulatory control of 20-hydroxyecdysone.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 14/07/20 alle ore 18:35:07