Glucocorticoid Binding by Human Fetal Membranes at Term

Cytosol preparations in Tris-buffer of human term amnion, choriodecidua, and decidua were incubated with [³H]dexamethasone for up to 24 h at 0 C. Under these conditions the specific binding of [³H]dexamethasone was low, ranging from 3–13 fmol/mg protein. Furthermore, when samples of whole choriodecidual homogenate were incubated with [³H]dexamethasone for 1 h at 37 C, there was no significant nuclear translocation of the steroid. In contrast to these findings, when cytosol preparations of sheep fetal lung were incubated with [³H]dexamethasone at 0 C, there was a rapid uptake of the steroid, reaching specific binding values of 399 ± 81 fmol/mg protein. The inclusion of sodium molybdate in the homogenization buffer led to an increased uptake of [³H]dexamethasone by amnion and choriodecidua; the specific binding ranged from 9–25 fmol/mg protein for cytosol and was 8 fmol/mg protein for nuclear preparations. Scatchard plot analysis of the data showed that both amnion and choriodecidua possess high affinity (K^d = 5–10 nivt), low capacity (50–170 pM) binding sites for [³H]dexamethasone. These findings suggest that the human fetal membranes at term contain specific glucocorticoid receptors, although in low concentrations compared to other glucocorticoid target tissues.