Does high polyunsaturated free fatty acid level at the feto-maternal interface alter steroid hormone message during pregnancy?

Polyunsaturated fatty acids (PUFA) are important in pregnancy, fetal develo pment and parturition. We measured free fatty acids (FFA), albumin and alph a-fetoprotein (AFP) in the maternal and fetal circulations of women undergo ing elective Caesarean section at term. We also studied the impact of PUFAs on estrogen (ER) and progesterone receptors (PR) binding properties in vit ro in the myometria of pregnant women and ex vivo in human myometrial cells in culture. FFA in intervillous blood (I) (feto-maternal interface) and maternal periph eral blood (M) were similar, while those in the umbilical vein (V) and arte ries (A) were 2-4 fold lower (P < 0.001). PUFA levels were low in M and 3 f old higher in I, A and V (P < 0.001); consequently C20:4 and C22:6 were mos t abundant in intervillous space. Albumin was uniformly distributed throughout the maternal-fetal unit, but t here was a transplacental gradient in AFP. The AFP in the intervillous space had a special conformation (less immune-r eactive, more anionic), suggesting loading with PUFA. Physiological concent rations of C20:4 stimulated estradiol binding, but inhibited progestin bind ing. C20:4 inhibited progesterone binding by decreasing the number of bindi ng sites, with no change in apparent affinity, in vitro in myometrial tissu e and ex vivo in myometrial cells. Thus PUFA may modulate the steroid hormo ne message, so that the high C20:4 concentration at the maternal-fetal inte rface at term may help amplify the estrogen signal and inhibit the progeste rone signal.