Tributyltin chloride exposure to post-ejaculatory sperm reduces motility, mitochondrial function and subsequent embryo development

Abstract

Context Male exposure to environmental toxicants can disrupt spermatogenesis and sperm function. However, consequences of environmentally relevant organotin exposure to post-ejaculatory mammalian spermatozoa on fertility are poorly understood. Aims Determine the consequences of tributyltin chloride (TBT) exposure on post-ejaculatory sperm function and subsequent embryo development. Methods Frozen-thawed bovine sperm were exposed to TBT (0.1–100 nM) for 90 min (acute) and 6 h (short-term) followed by quantification of multiple sperm kinematics via computer aided sperm analysis. JC-1 dye was used to measure mitochondrial membrane potential. Sperm were then exposed to TBT for 90 min in non-capacitating conditions, washed several times by centrifugation and applied to gamete co-incubation for in vitro embryo production to the blastocyst stage. Key results 100 nM TBT decreased total motility (88 vs 79%), progressive motility (80 vs 70%) curvilinear velocity and beat-cross frequency for 90 min with similar phenotypes at 6 h (P < 0.05). Sperm mitochondrial membrane potential was lower in 10 and 100 nM groups after 6 h (P ≤ 0.05). Embryos fertilised from TBT-exposed sperm had reduced cleavage rate (80 vs 62%) and 8–16 cell morula development (55 vs 24%) compared to development from unexposed sperm. Conclusions Exposure of post-ejaculatory mammalian sperm to TBT alters sperm function through lowered motility and mitochondrial membrane potential. Fertilisation of oocytes with TBT-exposed sperm reduces embryo development through mechanisms of paternal origin. Implications Acute and short-term environmental exposure of post-ejaculatory sperm to organotins and endocrine disrupting chemicals such as TBT contribute to idiopathic subfertility and early embryo loss.