Characterization of urinary metabolites of testosterone, methyltestosterone, mibolerone and boldenone in greyhound dogs

Androgenic steroids are used in female greyhound dogs to prevent the onset of estrus; moreover, these steroids also have potent anabolic activity. As anabolic steroids increase muscle mass and aggression in animals, the exces sive use of these agents in racing greyhounds gives an unfair performance a dvantage to treated dogs. The biotransformation of most anabolic steroids h as not been determined in greyhound dogs. The objective of the present stud y was to identify the urinary metabolites of testosterone, methyltestostero ne, mibolerone, and boldenone in greyhound dogs, These steroids were admini stered orally (1 mg/kg) to either male or female greyhound dogs and urine s amples were collected pre-administration and at 2, 4, 8, 12, 24, 72, and 96 h post-administration. Urine extracts were analyzed by high-performance li quid chromatography/mass spectrometry (HPLC/MS) to identify major metabolit es and to determine their urinary excretion profiles. Major urinary metabol ites, primarily glucuronide, conjugated and free. were detected for the sel ected steroids, Sulfate conjugation did not appear to be a major pathway fo r steroid metabolism and excretion in the greyhound dog. Phase I biotransfo rmation was also evaluated using greyhound dog liver microsomes from untrea ted dogs. The identification of several ill vivo steroid metabolites genera ted in this study will be useful in detecting these steroids in urine sampl es submitted for drug screening.