Boule, the ancestor of the DAZ (Deleted in
AZoospermia) gene family, in most organisms is mainly involved in male meiosis. The present study investigates the effects of the
plasticizer DEHP (50mg/kg
body weight) and
herbicide butachlor (0.39mg/L) on male rainbow trout (Oncorhynchus mykiss) for a 10-day period in two independent experiments. The results showed that plasma
testosterone (T) concentrations were significantly lower in fish exposed to either
DEHP or
butachlor compared to the control fish (P<0.05). Fish showed a significantly elevated hepatosomatic index (HSI) in the
butachlor treatment (P<0.05). However, no significant difference was observed in HSI values in the
DEHP treatment (P>0.05). In addition, no significant differences were found in the gonadosomatic index (GSI) in both
DEHP and
butachlor treatments (P>0.05). Histologically, testes of male trout in the control groups were well differentiated and filled with large numbers of cystic structures containing spermatozoa. In contrast, the testes of male trout contained mostly spermatocytes with few spermatozoa in both treated group, suggesting that
DEHP and
butachlor may inhibit the progression of meiosis. Also, boule gene expression was significantly lower in the testes of male trout affected by
DEHP and
butachlor in comparison with their control groups (P<0.05), which confirmed the meiotic arrest in affected trout. Based on the results, the present study demonstrated that
DEHP and
butachlor can inhibit the progression of spermatogenesis in male trout, potentially by causing an arrest of meiosis, maybe due to down-regulation of boule gene expression through T and/or IGF1 via ERK1/2 signaling in T-independent pathways. In addition, these results confirmed that boule can be considered as a predictive marker to assess meiotic efficiency.