LAUSR

Endocrine disruption potentials of phthalates have been widely recognized, but relatively little is known about relative potency of major phthalates. In the present study, six phthalates were chosen, i.e., dimethyl phthalate (DMP), diethyl phthalate (DEP), di(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DnOP), diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP), and their endocrine disruption effects were evaluated by employing two cell lines and an embryonic zebrafish assay. Binding affinity with estrogen receptors (ERs) and effects on steroidogenesis were evaluated with MVLN and H295R cell assays, respectively. In zebrafish embryos, transcription of genes regulating steroid hormone balance and estrogen receptors was measured. Exposure to DMP, DEP, DEHP, and DnOP significantly increased E2/T ratio in H295R cells. However, no significant binding affinity to ERs was observed in MLVN cells. Exposure to DEHP influenced the expression of vtg1, esr1, and cyp19a1b genes in zebrafish larvae. DMP, DEP, DINP, and DIDP exposure led to significant transcriptional changes even at lower exposure concentrations, suggesting their greater endocrine disruption potency than DEHP in zebrafish. Our findings demonstrate that endocrine disruption upon phthalate exposure varies between in vitro and in vivo assay, and a battery of tests are warranted to understand endocrine disruption potentials of phthalates. Consequences of long-term exposure to phthalates other than DEHP warrant further evaluations.