Vitreous structure, IV. Chemical composition of the insoluble residual protein fraction from the rabbit vitreous.

Analysis of the structural proteins in the rabbit vitreous showed that the hydroxyproline content was 3.1 per cent w/w compared to a value of 10.9 per cent w/w for equivalent samples obtained from cattle. In contrast to the discreet fibers in bovine vitreous, the rabbit constituents occur as an aggregate of fibrils with a diameter of 15 to 20 å. The amino acid and carbohydrate composition was similar to vascular basement membrane and isolated fractions contained significant amounts of palmitic and stearic acids. The data indicate that the variability of vitreous structure in different species is not only quantitative, but also qualitative. It is suggested that in the rabbit the structural proteins may be derived primarily from the atrophied hyaloid system and that little, if any, secondary vitreous formation occurs in this animal.