KERATAN SULFATE AND THE ULTRASTRUCTURE OF CORNEA AND CARTILAGE - A STAND-IN FOR CHONDROITIN SULFATE IN CONDITIONS OF OXYGEN LACK

  • 1 June 1988
    • journal article
    • research article
    • Vol. 158, 95-108
Abstract
Corneas from mouse, rat and rabbit were analysed quantitatively and qualitatively for collagen and acid glycosaminoglycans. They were examined by light and electron microscopy, using Alcian blue and Cupromeronic blue, in critical electrolyte concentration methods, with or without digestion by hyaluronidase, chondroitinases and keratanase, for their sulphated glycosaminoglycan distributions. Glycosaminoglycan patterns were very different in the 3 species. Mouse lacked chemically detectable keratan sulphate, which was present in considerable amounts in rat and rabbit stroma. Mouse corneal stroma proteoglycan filaments were located predominantly at the gap zone of the collagen fibrils, mainly at the d band, with few at the a and c bands. Rat and rabbit micrographs were more complicated, with many proteoglycan filaments at the a and c, as well as the d and e bands. These findings support the proposal that the a and c bands are specific binding sites for keratan sulphate proteoglycan. (Scott &O Haigh, Biosci. Repts. (1985) 5 765-774). Evidence from studies on cornea and cartilage suggests that keratan sulphate is produced in conditions of O2 lack, rather than chondroitin sulphate. Metabolic mechanisms which could account for this balance are proposed. The production of uridine diphosphate glucuronic acid is the key step, which is sensitive to hypoxia, lactate and NAD: NADH ratios.