Biosynthesis of basement membrane collagen by rabbit corneal endothelium in vitro

The synthesis of collagen has been demonstrated in endothelial cells of Descemet's membrane isolated from rabbit cornea. Incorporation of [¹⁴C]proline and [¹⁴C]lysine into nondialyzable protein was measured in the medium and cell fraction after incubating Descemet's membrane for up to 5 hours. In the [¹⁴C]collagen synthesized by the endothelium, 15% of the hydroxy[¹⁴C]proline was present as the 3 isomer. About 98% of the hydroxy[¹⁴C]lysine in the ¹⁴C labeled protein found in the medium was glycosylated; 95% of the glycosylated hydroxy[¹⁴C]lysine was in the form of the disaccharide glucosyl galactosylhydroxy[¹⁴C]lysine. Time course experiments with [¹⁴C]proline indicated that there was a delay of about 60 min before significant amounts of [¹⁴C]collagen were secreted into the medium. The initial polypeptides of [¹⁴C]collagen synthesized by the corneal endothelium had an apparent molecular weight of 155,000. The chemical and physical properties of the [¹⁴C]collagen synthesized by rabbit corneal endothelium are consistent with those of basement membrane collagen synthesized by other cell types.