The role of nonesterified fatty acids and of alpha 1-fetoprotein in estrogen-dependent endocrine systems.

We discuss the various experimental findings to date that indicate that AFP may be considered as a positive or negative modulator of estrogenic action. Moreover, we show that this protein, even when nonestrogenophilic, is able to bind other hydrophobic ligands, in particular nonesterified fatty acids. These fatty acids inhibit the binding of estrogens to murine AFP as well as to the cytosolic estrogen receptors. Thus, the AFPs of all species--whether or not estrogenophilic--might play an endocrinologic role through the intermediary of the unsaturated fatty acids to which they associate with high affinity.

[Inhibition of the uterine binding of estrogens by unsaturated fatty acids in immature female rats]. / Inhibition de la fixation utérine des aestrogènes par les acides gras insaturés chez la ratte immature.

We demonstrate that the interactions between the uterine cytosol proteins of 24 day old Rats and estradiol-17 beta (E2) are significantly influenced by physiological concentrations of non esterified fatty acids (2. 10(-4)M). We show that the specific binding of the hormone to the 8S uterine receptor, is markedly inhibited (50-80%) by the unsaturated fatty acids. The observed inhibition is a function both of acid dose and acid unsaturation degree. The polyunsaturated arachidonic and docosahexaenoic acids are the strongest inhibitors, whereas the saturated palmitic and stearic acids do not displace the E2 from the 8S receptor.