De Novo Synthesis of Placental Protein-14 (PP14) and not PP12 by Monolayer Cultures of Glandular Epithelium of Gestational Endometrium

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Abstract
Nine monolayer cell cultures of glandular epithelium from gestational endometrium were established from six apparently healthy women undergoing elective termination of pregnancy (7-11 weeks gestation). Radiolabel incorporation studies showed increasing incorporation of [36S]methionine into proteins present in supernatant and cytosol fractions over 48 h. The secreted proteins represented approximately 20% of the total incorporation of methionine into cytosolic proteins. De novo synthesis and secretion of placental protein-14 (PP14) and not PP12 was identified by a novel combination of line immunoelectrophoresis and autoradiography. All monolayer cultures demonstrated the presence of radiolabeled PP14, but not PP12, in the culture supernatants. These observations suggest that the glandular epithelial cells are the major site of synthesis and secretion of PP14 in human gestational endometrium.