Type II collagen in the early embryonic chick cornea and vitreous: Immunoradiochemical evidence

The relative proportion of collagen types I and II was examined in early chick corneas and vitrous bodies by radioimmunoprecipitation. Embryos (4–5 days of incubation) were labelled in ovo with ³H-proline. After an additional 1–2 days, corneas and vitreous bodies were removed and the collagen was extracted and treated by limited pepsinization. Then, the labelled collagens were reacted with affinity purified antibodies against collagen types I and II, and the immune complexes precipitated with protein A-containing Staphylococcus aureus. In some cases, the precipitated collagen was further analysed by SDS-polyacrylamide gel electrophoresis. The results for the vitreous showed that greater than 90% of the labelled material precipitated by the antibodies was in type II. In the corneal samples, on the other hand, both types of antibodies precipitated appreciable labelled collagen with somewhat less than half being type II (30–46%). These results are in agreement with our earlier biochemical observations on the relative content of type II collagen in these extracellular matrix-rich structures from embryonic avian eyes.