Placental proteins and steroid hormones in the soluble fraction of human syncytiotrophoblast plasma membrane

Abstract
Placental protein 5 (PP5), pregnancy-specific glycoprotein (SP1), pregnancy-associated .alpha.2-glycoprotein (SP3) and chorionic gonadotropin could not be demonstrated in the soluble fraction from microvillous plasma membrane preparations isolated from the syncytiotrophoblast of full-term human placentae. Progesterone, total estriol and placental lactogen may have some association with this membrane.