Production of Pregnancy-Specific β1-Glycoprotein by Cultured Placental Cells*

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Abstract
The synthesis of pregnancy-specific β1-glycoprotein (PSβG) was studied in simian virus 40 temperature-sensitive A mutant-transformed human first trimester and term placental cells. At the permissive temperature (33 C, transformed phenotype), they produced low levels of PSβG. At the restrictive temperature (40 C), the transformed phenotype was lost, and the production of PSβG was greatly enhanced. The PSβG produced by these transformed placental cells resembled the purified placental PSβG by several criteria. Both cell and placental PSβG bound to Concanavalin A-Sepharose and were, therefore, glycoproteins. The cell PSβG cochromatographed with placental PSβG on a Bio-Gel A-0.5m column. Furthermore, the slopes of the dose-response curves for the cell PSβG were indistinguishable from that for placental PSβG. The synthesis of PSβG at both 33 and 40 C in these placental cells was greatly induced by sodium butyrate and 5-bromo-2’- deoxyuridine. Sodium butyrate was a more effective inducer at 33 C, whereas BrdUrd appeared to be a better inducer at 40 C.