Atrazine and the hypothalamo-pituitary-gonadal axis in sexually maturing precocial birds: Studies in male Japanese quail

The herbicide atrazine is a putative endocrine disruptor. The present studies investigated the effects of atrazine in male Japanese quail during sexual maturation. Atrazine was administered for two weeks in the diet or systemically to birds under long photoperiods. Atrazine had no effect on mortality but depressed both feed intake and growth (average daily gain [ADG] in g/day) at dietary concentrations of 1000 ppm. Atrazine in the diet at 10 ppm, but at no other concentrations, increased testes weight and gonadal-somatic-index and decreased the seminiferous tubule diameter-to-testis weight ratio. However, there were no effects on absolute tubule diameter, relative stage of testicular development, or the presence of a lumen. Atrazine in the diet at 1000 ppm increased circulating concentrations of testosterone but this effect was not observed consistently in all studies. Dietary atrazine at 10 ppm increased circulating concentrations of estradiol. Moreover, in one study, atrazine at 1000 ppm in the diet decreased circulating concentrations of luteinizing hormone. Atrazine administered systemically exerted no effect on indices of growth or reproduction. Atrazine did not mimic the effects of either estradiol or tamoxifen in male quail; thus, atrazine did not exhibit overt estrogenic or anti-estrogenic activity. Conversely, atrazine augmented the effects of testosterone and estradiol on testis regression, presumably by increasing the negative-feedback effects of these sex-steroids on follicle stimulating hormone secretion. It is concluded that atrazine up to 1000 ppm in the diet may exert some effects on reproductive development in sexually maturing male birds, but these are inconsistent and modest.