Extracellular, surface, and intracellular proteoglycans produced by human embryo lung fibroblasts in culture (IMR-90).

Medium and cell-associated proteoglycans produced by human embryo lung fibroblasts (IMR-90) in culture were analyzed after 48-h uptake of N ~z ~~S O ~.The culture medium contained three proteoglycan fractions which could be separated from one another by density gradient centrifugation and gel chromatography under dissociative conditions.The most dense component eluted from Sepharose 2B with peak K,, = 0.40 and contained predominantly heparan sulfate chains with M, = 40,000.A somewhat less dense component had peak K,, = 0.29 and chondroitin sulfate chains with M, zz 40,000.The least dense proteoglycan (p < 1.46) was the predominant proteoglycan component of the medium.It eluted from Sepharose 2B at K,, = 0.68 and was composed primarily of dermatan sulfate-containing chains with M, = 25,000.Cell-associated proteoglycans were solubilized by treatment with a zwitterionic detergent followed by extraction in 4 M guanidine HCl.By Sepharose 2B chromatography, the cells contained a heparan sulfate proteoglycan fraction similar to the most dense component of the medium.This fraction was removed from the cell surface by trypsin treatment but was not significantly displaced by exogenous heparin.The cells also contained a smaller heparan-sulfate-containing component (Knv = 0.74) which was not sensitive to papain digestion or alkaline treatment and may not be a proteoglycan.This component was diminished by 50% during 24-h chase and probably represents an intracellular storage or degradation pool.