Introduction: Environmental chemicals (ECs) are associated with an increased incidence of testicular cancer and reduced sperm quality. Regional differences are thought to reflect different levels of EC exposure. Since the dog is a sentinel of human exposure, we hypothesised that geographical variation in testicular chemical profiles may be associated with altered reproductive development and/or function.
Methods: Canine adult testes (routine castrations) from UK (West Midlands (WM: n=12), East Midlands (EM: n=9) and South East England (SE: n=14)) and Scandinavian regions (Finland-Vantaa (FV: n=10) and DenmarkCopenhagen (DC: n=10)) were analysed for ΣPCB, ΣPBDE congeners and DEHP. WM canine ejaculates were analysed for 7 PCB and 7 PBDE congeners (n=14; 3 pools: n=5, 5 and 4 respectively). Testicular developmental markers were identified by immunohistochemistry: Vimentin (Sertoli cell), PCNA (Proliferation) and DAZL (Spermatogenesis).
Results: Ejaculate: 6 PCB and 4 PBDE congeners detected (PCB-28, 52, 101, 118, 138, 153; PBDE 28, 47, 99, 100). Testis: ΣPCB congeners greatest in WM (P≤0.0002), ΣPBDE congeners greatest in FV (P≤0.0014) and DEHP greatest in SE (P≤0.0001). Significant regional differences observed for developmental markers: i) Vimentin: Sertoli cell (SC) numbers (P≤0.0001) and %SC staining (P≤0.0001): EM greater and FV lower for both, ii) PCNA: Scandinavian regions < UK (P≤0.0001), iii) DAZL: FV < DC and UK regions (P≤0.0001). Testis ECs: ΣPBDE negative correlation with increased PCNA, DAZL, Vimentin and SC number (P≤0.05, r=0.43, 0.43, 0.50, 0.43 respectively), ΣPCB positive correlation with increased PCNA and DAZL cellular expression (P≤0.01, r=0.46, 0.47 respectively).
Conclusion: Chemical profiling of ECs in canine testis show i) regional variations and ii) correlations between EC concentrations and the expression of cellular or functional testicular markers. This may account for reported regional variations in male reproductive development.
11 Jul 2016 - 11 Jul 2016