Transferrin stimulates proteoglycan accumulation by fetal lung cells in culture

The role of transferrin in growth and the formation of extracellular matrix was investigated by comparing its effects on proteoglycan metabolism and cell proliferation in primary cultures of fetal rat lung fibroblasts and Type II epithelial cells. Transferrin specifically stimulated the accumulation of dermatan/chondroitin sulfate proteoglycans associated with the cells and matrix in a dose-dependent manner (0-200 micrograms/ml, r = .850 in fibroblasts and r = .810 in Type II cells). This effect was not due to increased synthesis since there was a corresponding decrease in proteoglycans and their degradation products released into the medium. The effect is probably mediated via an action on the proteoglycan core protein, since there was no effect of transferrin on enzyme activity promoting glycosaminoglycan synthesis on the synthetic initiator beta-D-xyloside. The effect of transferrin on proteoglycan distribution was not a secondary effect caused by changes in collagen synthesis and was not linked to cell proliferation or the concentration of Fe3+ ions in the culture medium.