Binding of alkylphenols and alkylated non-phenolics to rainbow trout (Oncorhynchus mykiss) hepatic estrogen receptors

Alkylphenols are well-known endocrine disrupters, mediating effects through the estrogen receptor (ER). In the present work, the interaction of alkylphenols and alkylated non-phenolics with hepatic rainbow trout (Oncorhynchus mykiss) estrogen receptors (rtERs) was determined. The role of alkyl chain length and branching, substituent position, number of alkylated groups, and the requirement of a phenolic ring structure was assessed. The results showed that the rtERs bound most alkylphenols, although with 20,000 to 2 million times lower affinity than the endogenous estrogen 17β-estradiol. Mono-substituted alkylphenols with moderate (C4–C6) and long (C8 and C12) alkyl chain length in the para position exhibited the highest affinity for the rtERs. Substitution with multiple alkyl groups, presence of substituents in the ortho- and meta-position, and lack of a hydroxyl group on the benzene ring reduced the binding affinity. The rtERs resembled the reported binding specificity of the human ER for alkylphenols, although some exceptions were identified.