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

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. Environmental contaminant exposure to humans and animals is a global concern for negative effects on reproductive health and fertility. Consequences of the common and environmentally stable compound tributyltin chloride on post-ejaculatory sperm exposure were previously unknown and established herein to alter sperm function through reducing embryo development. These findings indicate that short-term exposure to environmental contaminants impact male fertility through a mechanism of paternal origin that negatively alters embryo development. [ABSTRACT FROM AUTHOR]