Proteoglycans of rabbit cornea: labelling in organ culture and in vivo.

Rabbit corneas maintained with radioactively-labelled precursors in organ culture for up to 42 hr produced labelled proteoglycans of the same kind as those that exist normally or that are produced by labelling in vivo. Whole corneas, including a narrow strip of sclera, were kept in culture in the presence of [3H]-glucosamine and [35S]-sulfate. The rate of incorporation of sulfate into extractable proteoglycans was linear over the time investigated, as was the rate of incorporation of glucosamine after a short lag. Three labelled proteoglycans were isolated and found to behave in ion-exchange chromatography and gel chromatography in the same way as they did in previous studies by chemical analysis. Their labelled glycosaminoglycans were primarily dermatan sulfate and keratan sulfate, with traces of hyaluronic acid and heparan sulfate. When labelled precursors were injected directly into the anterior chamber of rabbit eyes, the resulting labelled proteoglycans were similar to those obtained in organ culture. Both in vivo and during organ culture, the specific activity of hexosamine in the keratan sulfate proteoglycans was about one-half that in dermatan sulfate, probably because of different synthetic rates or different specific activities of immediate precursors.