Biosynthesis of sulphated macromolecules by rabbit lens epithelium. I. Identification of the major macromolecules synthesized by lens epithelial cells in vitro.

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Abstract
Rabbit lens epithelial cells synthesize and secrete a variety of [35S]sulfate-labeled glycoconjugates in vitro. Associated with the cell layer, and with the medium, was a high MW glycoconjugate(s) that contained heparan sulfate which was apparently covalently linked to sulfated glycoprotein. This component(s) was eluted in the void volume of a Sepharose CL-2B column and could not be fractionated by detergent treatment or extraction with lipid solvents. The cell layer also contained glycosaminoglycans (72% heparan sulfate, 28% chondroitin sulfate), as well as a small proportion of a low MW sulfated glycoprotein. The major 35S-labeled species secreted into the medium were sulfated glycoproteins with approximate MW of 120,000 and 35,000 together with a heparan sulfate proteoglycan. This proteoglycan could be precipitated from the culture medium with 30% saturated (NH4)2SO4 and eluted from Sepharose CL-4B columns at approximately the same position (Kav [distribution coefficient] = 0.15) as heparan sulfate proteoglycans described in the basement membrane of the EHS sarcoma and of the mouse mammary epithelium. Its presence in the culture medium was unanticipated but may be explained by the inability of these cultures to deposit a basement membrane when grown on a plastic surface.