In Vitro Metabolism of Doping Agents (Stanozolol, LGD-4033, Anastrozole, GW1516, Trimetazidine) by Human Seminal Vesicle and Liver Fractions.

Background: In order to address complex scenarios in anti-doping science, especially in cases where an unintentional exposure of athletes to prohibited substances and a corresponding contamination of doping control samples at the collection event are argued, an understanding of tissue-specific drug metabolism is essential. Hence, in this study, the metabolic capacity of the seminal vesicle using in vitro assays was investigated. Methods: The aim was to assess whether selected doping-relevant substances-stanozolol, LGD-4033, GW1516, trimetazidine, and anastrozole-are metabolised in seminal vesicle cellular fractions (SV-S9) and how that metabolism compares to biotransformations induced by human liver S9 fractions (HL-S9). Liquid chromatography coupled to high-resolution/accurate mass spectrometry (LC HRAM MS) enabled the sensitive detection and identification of metabolites, revealing a limited metabolic activity of SV-S9. Results: For LGD-4033, GW1516, and trimetazidine, minor metabolic transformations were observed, whereas no metabolites of stanozolol or anastrozole were detected. Gene expression analysis using digital polymerase chain reaction (dPCR) confirmed transcripts of CYP2D6, CYP2E1, and CYP2C9 in SV-S9, though no enzymatic activity was detected. Gene expression and enzymatic activity in CYP3A4 and CYP1A2-major hepatic enzymes-were absent in SV-S9. Conclusions: Overall, these pilot study results suggest that the seminal vesicle has only a low capacity for xenobiotic metabolism, which translates into a limited role in the biotransformation of drugs and, hence, the metabolic pattern.