Possible evidence that dehydroepiandrosterone sulfate (DHA-S) stimulates cervical ripening by a membrane-mediated process: specific binding-sites in plasma membrane from human uterine cervix.

Fetal adrenal steroid, dehydroepiandrosterone sulfate (DHA-S) is well known to promote cervical ripening in late pregnancy. The presence of sites specifically binding the DHA-S in plasma membrane was studied in human cervical fibroblasts prepared from pregnant uterus. The fibroblasts were incubated with [3H] DHA-S and then fractionated into plasma membranes, cytosol, nuclei, and other organella debris. The specific activity of 3H-count in the plasma membrane fraction was enriched approximately 7-fold compared with the whole homogenate. When the isolated plasma membrane preparations from the fibroblasts were exposed to [3H] DHA-S, the binding showed saturation kinetics; an apparent equilibrium dissociation constant (Kd) of 12 nM, and the binding capacity (Bmax) of 1.25 pmol/mg protein. The present results suggest that DHA is bound to and recognized by components in plasma membrane, and may exert its action on cervical ripening through the membrane-mediated processes.