LIQUID-CHROMATOGRAPHIC SEPARATION AND GAS-CHROMATOGRAPHIC MASS-SPECTROMETRIC DETERMINATION OF 17-ALPHA-METHYLTESTOSTERONE RESIDUES EXTRACTED FROM RAINBOW-TROUT TISSUES

The residues of [H-3]-17-methyltestosterone (17MT) in rainbow trout after a single intragastric dose (200 mug, 0.37 MBq) were investigated. The metabolites were extracted from liver and carcass with chloroform-methanol (2 + 1, v/v). After enzymatic hydrolysis of the glucuronides, unconjugated steroids and aglycones were chromatographed by reversed-phase liquid chromatography. Each labelled fraction was collected and analysed by gas chromatography-mass spectrometry. After 24 h, the liver contained 4% of the administered dose. In the hepatic unconjugated and aglycone fractions the major metabolite was an isomer of 17alpha-methylandrostane-3xi,16xi,17beta-triol. 7alpha-Hydroxy-17alpha-methyl-androstane-3alpha,17beta-diol was also observed in the unconjugated fraction. In addition to these metabolites, unchanged 17MT, 17alpha-methyl-5beta-androstane-3alpha,17beta-diol and 17beta-hydroxyandrosta4,6-dien-3-one were identified in the unconjugated fraction extracted from carcass samples. After 72 h, 7alpha-hydroxy-17alpha-methylandrostane-3alpha,17beta-diol persisted to a significant extent in carcass samples whereas no trace of 17MT was detected. This metabolite could therefore be used as an indicator of the administration of 17MT in fish.