Species specificity of triphenylethylene derivatives and of compounds with a steroidal backbone for human and rat liver antioestrogen binding site (AEBS).

The binding affinity of derivatives of the triphenylethylene (TPE) antioestrogen tamoxifen and of steroidal compounds for human liver antioestrogen binding sites (AEBS) was compared with their binding affinity for rat liver AEBS. Despite the observation of some quantitative differences overall a highly significant correlation between the relative binding affinity (RBA) for human and rat liver AEBS was found for all compounds tested (r = 0.93, N = 19, P < 0.001). This was more pronounced for TPE derivatives (r = 0.83, N = 12, P < 0.01) than for cholesterol derived compounds (r = 0.64, N = 7, not significant). We conclude that AEBS from rat liver can be used instead of human livers as a model to study the interactions of antioestrogens with AEBS.