The variation of the glycosaminoglycans of the canine intervertebral disc with ageing. I. Chondrodystrophoid breed.

The variation with age and spinal level of the glycosaminoglycan distribution in beagle (a chondrodystrophoid breed) intervertebral discs have been assessed by means of histochemical and chemical methods. Chondroitin sulphate is the major glycosaminoglycan of the immature beagle disc, but with ageing, this is partially replaced by keratosulphate. The level of glycosaminoglycans in the nucleus pulposus is markedly less than in the nonchondrodystrophoid breed and by 1 year of age, the beagle nucleus pulposus has become largely fibrocartilagious. This alteration in 'normal' disc developments is possibly associated with the elevated incidence of disc disorders in the chondrodystrophoid breeds.