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 (Kd = 5-10 nM), 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.