In vitro modulation of prolactin mRNA by toxaphene and 3,3′,4,4′-tetrachlorobiphenyl

It is now well recognized that many environmental contaminants are capable of disrupting endocrine processes in a variety of species, including birds, mammals, reptiles, and fish. Among these contaminants are toxaphene and polychlorinated biphenyls (PCBs), two of the most prevalent contaminants present in aquatic food chains of the Great Lakes and the Canadian Arctic region. We set out to investigate the possible endocrine-modulating activities of toxaphene, the PCB congener 3,3′,4,4′-tetrachlorobiphenyl (TeCB), an equimolar mixture of both compounds (toxaphene/TeCB), and estradiol (E2) (E2/toxaphene, E2/TeCB) on prolactin (PRL) mRNA expression. Concentrations ranging from 10−7 to 10−11 M for both toxaphene and TeCB were assayed but only toxaphene modulated PRL mRNA levels, as determined by relative quantitative reverse transcriptase-polymerase chain reaction. Maximal induction by toxaphene was seen at 10−7 M, resulting in a fourfold increase in PRL mRNA levels. No interactions were observed for combinations of the test substances. Our study demonstrates that toxaphene may exhibit estrogen-like activity by modulating PRL mRNA levels in GH3 cells.