The placenta as a glucocorticoid target tissue: exchange assay of (3H)-dexamethasone binding and effect of steroids on receptor content.

摘要: Binding of (3H)-dexamethasone was studied in high speed supernatant (HSS) basal zone trophoblast and labyrinthine rat placenta using an exchange assay. The system showed the following characteristics: (1) maximum binding attained after 120 min incubation; (2) molybdate required medium to measure sites at 20 degrees C equilibrium conditions; (3) near 90-100% between ligand corticosterone added during a preincubation; (4) low capacity (190-250 fmoles/mg protein), affinity (Kd 10(-8) M) binders were determined by saturation analysis; (5) competition with other steroids vitro revealed that trophoblast, only dexamethasone displaced ligand, whereas corticosterone, progesterone testosterone competed smaller degree than dexamethasone. We have also effect vivo treatment pregnant rats for four days dexamethasone, estradiol, or testosterone, on binding. Of all tested compounds, (which suspended 24 h before experiment prevent receptor occupancy exogenous hormone) significantly decreased tritiated hormone HSS trophoblast. These results suggest regulates its own placenta. physiological aspect this phenomenon requires elucidation role glucocorticoids placental function rat.