Synthesis of glycosaminoglycans by chick retinal pigment epithelium in vitro.

Cultured chick embryonal retinal pigment epithelial (RPE) cells synthesized two main glycosaminoglycans (GAGs), chondroitin 4-sulfate, and heparan sulfate. Chondroitin 4-sulfate was liberated mainly in the medium (apical side) and heparan sulfate was incorporated into the cell and/or basement membrane. Glycosaminoglycans liberated into the medium were composed of chondroitin 4-sulfate (44%), keratan sulfate (22%), heparan sulfate (18%) and hyaluronate (12%). On the other hand, the GAGs in the cell and/or basement membrane were composed of heparan sulfate (52%), hyaluronate (19%), and chondroitin 4-sulfate (13%).