Effect of atrazine metabolite, DACT, on sperm mitochondrial function and acrosome reaction – the bovine model

Abstract

Atrazine (ATZ) is one of the most extensively used herbicides. It is known as a ubiquitous environmental contaminant, and is considered an endocrine disruptor that adversely affects reproductive tissues. ATZ is frequently detected in ground and surface water. Once it enters the body, ATZ metabolized into various metabolites, which are further detected in the urine, serum and tissues. In mammals, the major ATZ metabolite is diaminochlorotriazine (DACT). Our aim was to explore the risk associated with exposure to DACT on sperm quality and fertilizing competence. Sperm from fresh ejaculates (‘Sion’) or isolated from testis epididymis compartments (head, body and tail) were capacitated in the absence or presence of 1, 10 or 100 µM DACT for 4 h. Following capacitation, acrosome reaction (AR) was induced by Ca++ ionophore. The integrity of the plasma and acrosome membranes and mitochondrial membrane potential (ΔΨm) were examined simultaneously by fluorescent staining after 0, 2 and 4 h of incubation. The proportion of sperm that underwent pseudo or induced AR was calculated. DACT reduced sperm viability at all examined concentrations and in all fractions. DACT (1 µM) impaired ΔΨm in sperm isolated from the epididymis tail and ejaculate (P < 0.005). DACT at 100 µM induced pseudo-AR in sperm isolated from the epididymis tail (P < 0.05), but not in ejaculated sperm. Induction of AR by Ca++ ionophore was impaired in ejaculated sperm exposed to 10 or 100 µM DACT (P < 0.05) and in sperm isolated from the epididymis tail and exposed to 1, 10 or 100 µM DACT (P < 0.0004). These findings expose the harmful effects of DACT on sperm viability, acrosome integrity and mitochondrial function, mainly at low, ecologically relevant, concentrations. We postulate that DACT-induced impairment of the AR involves alterations in sperm membranes and mitochondrial function.