BACKGROUND Cultured bovine corneal endothelial cells (CEC) synthesize heparan sulfate and dermatan sulfate containing proteoglycans and distribute them between different compartments. RESULTS [35S]sulfate labelled proteoglycans are found associated with the cell layer, secreted into the culture medium and deposited into the underlaying extracellular matrix. In the presence of basic fibroblast growth factor (bFGF)-a strong mitogen for CEC-subconfluent cells incorporate [35S]sulfate into the sulfated proteoglycans at a rate three times higher as compared with the proteoglycans of CEC in the absence of bFGF. The enhanced proteoglycan synthesis is accompanied with a shift in the proteoglycan distribution pattern. While in control cells the cell-associated heparan sulfate accounts for about 30% of the total glycosaminoglycans under the influence of bFGF the HS percentage increases to approximately 60%. CONCLUSIONS CEC synthesize and deposit endogenous bFGF into the extracellular matrix. Heparitinase treatment of the extracellular matrix releases bFGF activity which is able to stimulate the 35S incorporation into proteoglycans in a comparable manner as exogenous bFGF but does not influence the proteoglycan distribution pattern. Pretreatment of the matrix-bound bFGF activity with polyclonal antibodies against bFGF abolishes its stimulating activity.