Metabolism of methyltestosterone in the greyhound

Abstract

Gas chromatography/mass spectrometry and selective derivatisation techniques have been used to identify urinary metabolites of methyltestosterone following oral administration to the greyhound. Several metabolites were identified including reduced, mono-, di- and trihydroxylated steroids. The major metabolites observed were 17alpha-methyl-5beta-androstane-3alpha-17beta-diol, 17alpha-methyl-5beta-androstane-3alpha,16alpha,17beta-triol, and a further compound tentatively identified as 17alpha-methyl-5z-androstane-6z,17beta-triol. The most abundant of these was the 17alpha-methyl-5beta-androstane-3alpha,16alpha,17beta-triol. This metabolite was identified by comparison with a reference standard synthesised using a Grignard procedure and characterised using trimethylsilyl (TMS) and acetonide-TMS derivatisation techniques. There did not appear to be any evidence for 16beta-hydroxylation as a phase I metabolic transformation in the greyhound. However, significant quantities of 16alpha-hydroxy metabolites were detected. Selective enzymatic hydrolysis procedures indicated that the major metabolites identified were excreted as glucuronic acid conjugates. Metabolic transformations observed in the greyhound have been compared with those of other mammalian species and are discussed here.

Metabolism of stanozolol: Chemical synthesis and identification of a major canine urinary metabolite by liquid chromatography–electrospray ionisation ion trap mass spectrometry

“…An aqueous suspension of stanozolol (Stanabolic ® , Ilium, NSW, Australia; 1.4 mL = 70 mg stanozolol) was administered by intramuscular injection to one male greyhound (5 years, 35 kg). Urine samples were collected preadministration, then at 6 h post-administration, then on days 1, 2, 3,4,7,8,9,10,11,14,21 and 29 post-administration. All samples were stored frozen until required for analysis.…”

“…In the context of sporting pursuits, the metabolism of anabolic-androgenic steroids in humans [1,2] and horses [3] has been the subject of numerous detailed studies, leading to the development of a range of reference materials and robust drug screens. However, much less is known about the canine metabolism of this class of drugs [4][5][6][7][8][9].…”

Metabolism of norethisterone in the greyhound

“…. The 17α‐ethynyl function appears to impart a significant degree of stability to the structure resulting in the intense m / z 431 ion, in contrast to the fully saturated '‐diol' metabolites which normally exhibit a considerably greater degree of fragmentation than that observed here . Both metabolites were detected exclusively in the glucuronide fraction (see Table ).…”

“…Acetonide‐tms derivatives were prepared using a previously described procedure . 16β‐Hydroxytestosterone internal standard was added to each sample prior to derivatisation in order to demonstrate the efficiency of acetonide derivative formation.…”

“…The metabolism of norethisterone has not been previously investigated in the greyhound and this paper represents the first such study. It has been noted in previous greyhound steroid metabolism studies that liquid chromatography/mass spectrometry (LC/MS) is not suitable for the analysis of saturated steroid metabolites . Gas chromatography/mass spectrometry (GC/MS) and selective derivatisation techniques have therefore been used to identify urinary metabolites of norethisterone following oral administration to the greyhound.…”