Evidence of boldenone, nandrolone, 5(10)-estrene-3β-17α-diol and 4-estrene-3,17-dione as minor metabolites of testosterone in equine.
The detection of boldenone, nandrolone, 5(10)-estrene-3β,17α-diol, and 4-estrene-3,17-dione in a urine sample collected from a gelding having been treated with testosterone (500 mg 'Testosterone Suspension 100', single dose, injected intramuscularly) in 2009 led the authors' laboratory to suspect that these 'testicular' steroids could be minor metabolites of testosterone in geldings. Administration trials on six castrated horses with Testosterone Suspension 100 confirmed that low levels of boldenone, nandrolone, 5(10)-estrene-3β,17α-diol, and 4-estrene-3,17-dione could indeed be detected and confirmed in the early post-administration urine samples from all six geldings. Although boldenone has been reported to be present in urine after testosterone administration, there has been no direct evidence reported that boldenone, nandrolone, 5(10)-estrene-3β,17α-diol, and 4-estrene-3,17-dione are metabolites of testosterone in geldings. Subsequent in vitro experiments involving the incubation of testosterone with horse liver microsomes, liver, adipose and muscle tissues, and adrenal cortex homogenates failed to provide evidence that these four substances are minor metabolites of testosterone. An administration trial using 'Testosterone Suspension 100' supplemented with13C-labelled testosterone (500 mg, 1:1 ratio, injected intramuscularly) was performed. The similarities of the excretion curves of12C-testosterone and13C-testosterone in urine suggest that there was minimal kinetic isotope effect.13C-Labelled boldenone, nandrolone and 4-estrene-3,17-dione were detected but not 5(10)-estrene-3β,17α-diol and its13C-counterpart. This is the first unequivocal evidence of boldenone, nandrolone and 4-estrene-3,17-dione being metabolites of testosterone in geldings. In view of these results, caution should be exercised when interpreting findings of boldenone, nandrolone and/or 4-estrene-3,17-dione together with a relatively high level of testosterone in gelding urine. Copyright © 2017 John Wiley & Sons, Ltd.
Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N.T, Hong Kong, China.
Jenny K Y
http://orcid.org/0000-0001-8245-6770
JKY
Wong
Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N.T, Hong Kong, China.
David K K
DKK
Leung
Department of Veterinary Regulation & International Liaison, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N.T, Hong Kong, China.
Peter
P
Curl
Department of Veterinary Regulation & International Liaison, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N.T, Hong Kong, China.
Peter J
PJ
Schiff
Department of Veterinary Regulation & International Liaison, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N.T, Hong Kong, China.
Kenneth K H
KKH
Lam
Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N.T, Hong Kong, China.
Terence S M
http://orcid.org/0000-0003-3779-2649
TSM
Wan
D000818:Animals; D004300:Doping in Sports; D004963:Estrenes / Q000032:analysis* / Q000737:chemistry; D006736:Horses; D008862:Microsomes, Liver / Q000737:chemistry / Q000378:metabolism*; D009277:Nandrolone / Q000032:analysis* / Q000737:chemistry; D013739:Testosterone / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*
D004963:Estrenes; D013739:Testosterone; C013915:boldenone; D009277:Nandrolone
13C-testosterone; equine; in vivo metabolite; mass spectrometry; steroids