Measuring ECM protein

[Fran Quero]

Hi all, i´m working with a fibroblast protein in my reseach and i want to measure if this protein is being secreted to the extracellular matrix. We already know that this protein is inside the cell so we dont want to contaminate the results with the endocellular proteing. We are measuring it with western blots but we need a protocol to isolate only the extracellular medium from a fibroblast culture. Any ideas?

Thank you for the help.

Fran.