THE EFFECT OF PLACENTA ON LACTOGEN RECEPTOR

This study examines the effect of placenta on the evolution of lactogen r eceptor in virgin pseudopregnant rabbit ovary, adrenal gland and mammary gland. Pseudopregnancy was induced with human chorionic gonadotropin. Does were injected with vehicle or placenta daily beginning on day six of the pseudopregnancy. Vehi- cle-t reated r abbits d uring pseudopregnancy demonstrated a peak of ovarian lactogen receptor on day eight of pseudopregnancy. After treatment with placental homogenate a shift of this peak to twenty days of pseudopregnancy occurred. Lactogen receptor i n adrenal and mammary gland membranes had peak receptor concentrations on day 14 of pseudopregnancy. Injection of placenta induced a shift to day 17 and days 17-20 in mammary and adrenal membranes, re- spectively. Serum concentrations of progesterone, estradiol, 20a dihydroprogester one and prolactin in placenta-treated groups xere not significantly different from those of vehicle-treated groups. Treatment of pseudopregnant does with a composite of hormones at the concentrations found in placental homogenate produced no modulation of tissue lactogen receptor. F ractionation of 20-day pregnant rabbit placenta revealed that 80:: of this activity could be found in the acetone extract vhiie 20% was in the bicarbonate extract. These observations s uggest that increases of lactogen receptor in ovary, adrenal and manmary glands o ccur during pseudopregnancy in rabbits and it is further concluded that placenta can alter these receptor induction paLtems to ones similar to those seen in these tissues during pregnancy.