Production of pregnancy-specific beta 1-glycoprotein by human placental cells and human fibroblasts.

The synthesis and regulation of pregnancy-specific beta 1-glycoprotein (PS beta G) in secondary placental cells and human fibroblasts was studied in vitro. Both types of cells produced PS beta G in culture. The secondary placental cells, however, produced considerably higher levels of PS beta G than did the human fibroblasts in both the absence and presence of inducers. The PS beta G produced by the secondary placental cells resembled the purified placental PS beta G in chromatographic behavior, immunological reactivity, and affinity to concanavalin A. The synthesis of PS beta G in the secondary placental cells and human fibroblasts was induced by sodium butyrate and 5-bromo-2'-deoxyuridine (BrdUrd) but was not affected by agents that increase intracellular cAMP concentrations and retinoic acid. The synthesis of two other placental markers, human chorionic gonadotropin (hCG) and the alpha subunit of hCG (hCG alpha), was also studied in both types of cells. Neither the secondary placental cells nor the human fibroblasts secreted hCG in vitro. The human fibroblasts also did not secrete hCG alpha both in the absence and presence of inducers. The secondary placental cells, however, secreted low levels of hCG alpha in the absence of inducer and high levels of hCG alpha in the presence of 8-bromo-cAMP (8BrcAMP), cholera toxin, and methylisobutylxanthine (MIX). The presence of PS beta G in secondary placental cells and human fibroblasts suggests that PS beta G may be associated with growth and maintenance of nontransformed cells in vitro.