The molecular weight of hyaluronate in the aqueous humour and vitreous body of rabbit and cattle eyes.

The molecular weight distribution of hyaluronate in the aqueous humour and vitreous body of rabbit and cattle has been determined by gel chromatography. The eluate from the column was monitored by a radioassay, whereby the molecular weight distribution of 15-20 microgram samples could be analysed. Control experiments were carried out with radioactively-labelled hyaluronate added to bovine material to estimate the degradation of the polymer during handling of the ocular fluids. It was shown that in vitro degradation does not appreciably affect the results. The analyses show a considerable polydispersity of the hyaluronate preparations. There is also a marked variation in the degree of polymerization between the two species. Hyaluronate from rabbit vitreous has a weight-average molecular weight (MW) of 2-3 X 10(6) while adult bovine vitreous displays a value of about 5-8 X 10(5). The hyaluronate of bovine vitreous varies with age. In newborn calf, a value of 3 X 10(6) was registered. This value dropped to about 5 X 10(5) in old cattle. The hyaluronate in the aqueous humour of rabbit showed a considerably higher molecular weight than that of the vitreous indicating that part of the hyaluronate in the anterior segment originates elsewhere than the vitreous. The differences between hyaluronate from the aqueous humour of adult cattle and that from the vitreous were more complex. As with the rabbit, a relatively large proportion of hyaluronate in the aqueous humour was of high-molecular weight, but, in contrast, the aqueous humour also contained material which had a lower degree of polymerization than the hyaluronate in the vitreous. The proportion of high-molecular weight material in bovine aqueous humour seemed to be lower in the summer than in the winter.