Di-(2-ethyl-hexyl) phthalate (DEHP) is the most commonly used plasticizer, interfering with fertility in the rat and mouse for both females and males. The reproductive toxicity of DEHP is attributable to the action of its primary metabolite, mono-(2-ethyl-hexyl) phthalate (MEHP). We examined the effects of MEHP on the activity and mRNA levels of aromatase as well as estradiol production on cultured bovine granulosa cells. Estradiol production was significantly decreased by the addition of 10 and 100 mM MEHP to the culture medium compared with no addition. Aromatase activity was significantly decreased by the addition of MEHP at 10, 50 and 100 mM compared with the controls. Aromatase mRNA was significantly decreased at 50 and 100 mM MEHP compared with the controls. These data suggest that the suppression of estradiol production by MEHP is likely mediated through the action of MEHP on transcriptional levels of aromatase in bovine granulosa cells, as well as in the rat. (Theriogenology Section, Department of Production Diseases TEL +81-29-838-7784)
