Comparison of production of choriogonadotropin inhibitory protein, prolactin and insulin-like growth factor binding protein-1 by human decidua in vitro.

Abstract

We have previously demonstrated that human decidua produces a protein (decidual choriogonadotropin inhibitory protein, DCIP) that inhibits human chorionic gonadotropin (hCG) secretion from primary trophoblasts and JEG-3 choriocarcinoma cells. The present study was undertaken to examine the relationship of DCIP production to that of cell protein, prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP-1). Term decidual cells, isolated from placental membranes by enzyme digestion and density gradient centrifugation, were incubated for 12 days in serum-free CMRL-1066 medium which was changed daily. At the end of each experiment the DCIP in the decidual culture medium was measured by bioassay: the percentage reduction, from control, of hCG production by JEG-3 cells exposed to 30% DCIP-containing decidual culture medium. Prolactin, IGFBP-1 and hCG were measured by radioimmunoassay. The DCIP activity was maximal during the first 3 days in culture. The bioactivity of decidual culture medium collected after the 5th day of culture gradually decreased and medium obtained from the final day of culture actually stimulated hCG secretion in the bioassay. Decidual cell protein gradually declined from 100% on day 1 to 56% on the last day of culture. The concentrations of protein, PRL and IGFBP-1 in the decidual culture medium gradually decreased during the first 4-6 days, followed by a rise. In contrast, glucose increased with time in culture. Production of PRL, IGFBP-1 and decidual culture medium protein exhibited a significant quadratic effect over the 12 days in culture. There was a negative relationship between decidual cell protein and glucose (r = -0.95) and a positive correlation between cell protein and protein in the decidual culture medium (r = 0.58). The DCIP activity was related to cell protein (r = 0.39), protein concentration in decidual culture medium (r = 0.36), and inversely related to the glucose level (r = -0.41). There was no relationship between DCIP activity and PRL or IGFBP-1. These results indicate that maximal DCIP production occurs during the first several days in short-term culture of decidual cells and is related to decidual-cell viability. As decidual-cell viability decreases, there is less glucose consumption in the decidual culture medium and the higher glucose levels may be responsible for the stimulatory effect of medium collected at the end of the study on JEG-3 hCG secretion.