Environmental chemicals impact dog semen quality in vitro and may be associated with a temporal decline in sperm motility and increased cryptorchidism.

Richard G Lea,Stewart M Rhind,Rebecca N Sumner,Andrew S Byers,Zulin Zhang,Gary C W England,Rachel Moxon,Sarah L Freeman,Martin Green,Jim Craigon,Holly M Richardson

doi:10.1038/srep31281

Abstract

Adverse temporal trends in human semen quality and cryptorchidism in infants have been associated with exposure to environmental chemicals (ECs) during development. Here we report that a population of breeding dogs exhibit a 26 year (1988–2014) decline in sperm quality and a concurrent increased incidence of cryptorchidism in male offspring (1995–2014). A decline in the number of males born relative to the number of females was also observed. ECs, including diethylhexyl phthalate (DEHP) and polychlorinated bisphenol 153 (PCB153), were detected in adult dog testes and commercial dog foods at concentrations reported to perturb reproductive function in other species. Testicular concentrations of DEHP and PCB153 perturbed sperm viability, motility and DNA integrity in vitro but did not affect LH stimulated testosterone secretion from adult testis explants. The direct effects of chemicals on sperm may therefore contribute to the decline in canine semen quality that parallels that reported in the human.

Highlights

Adverse temporal trends in human semen quality and cryptorchidism in infants have been associated with exposure to environmental chemicals (ECs) during development
Since human testicular dysgenesis syndrome” (TDS) includes a reduction in sperm count[21] and an increased incidence of cryptorchidism, we hypothesised that the dog may exhibit similar manifestations of TDS and that this may be associated with exposure to endocrine disrupting chemicals
In some years semen quality parameters temporarily increased as noted in other studies[22], there was a repeated decline in motility even after removal of animals with the poorest semen quality

Summary

Introduction

Adverse temporal trends in human semen quality and cryptorchidism in infants have been associated with exposure to environmental chemicals (ECs) during development. Reports of declining sperm counts linked with epidemiological data on increased incidences of testicular cancer and genital tract abnormalities, is indicative of an adverse environmental effect on male reproduction[6,7,8]. Since these reproductive problems, termed by some as “testicular dysgenesis syndrome” (TDS), cluster in geographical areas[9] they are thought to have a common aetiology and have been associated with endocrine perturbations in early life[10]. The effects of chemicals, at testicular concentrations, were tested on endocrine and sperm function in vitro

Methods

Results

Conclusion