Microchemical analysis of glycosaminoglycans, collagen, total protein and water in histological layers of nasal septum cartilage

Abstract

1. (1) Samples of the nasal septum cartilage from horses of various age groups (newborn, 1–3 years, >8 years) were prepared by serial sectioning; alternate sections were used for chemical analysis and histological control. 2. (2) Glycosaminoglycans were separated (after proteolytic digestion) by fractional elution of their cetylpyridinium complexes and the hexosamine content of the fractions was determined. The total values ranged from 2% hexosamine at the periphery (1st layer) to 12% in the middle zone (2nd layer), with slightly lower figures in the central (3rd) layer in old animals. The cetylpyridinium complexes of the major fraction varied in MgCl 2 from 0.3 to 0.6 M and showed solubility profiles with several peaks, different for the various layers. 3. (3) On the basis of macro-fractionation of pooled dissected layers, the fractions of the major glycosaminoglycan were identified as chondroitin 4-sulfate; they differed only slightly in sulfate content and showed a negligible contamination with amino acids. Differences in the molecular weight were observed and found to be related to the heterogeneity as revealed by the fractionation procedure. 4. (4) Two minor glycosaminoglycan fractions were observed; they did not show variation in the different layers and are tentatively suggested to be keratan sulfate and hyaluronic acid. 5. (5) Both the collagen and non-collageneous protein show the highest concentration at the periphery of the nasal septum cartilage and decrease markedly towards the center; their ratio is approximately constant, with the exception of the 3rd layer in old animals, where the non-collagenous protein rises markedly to over 40% of the dry weight. 6. (6) The water content in the peripheral layers of the nasal septum is higher than in the middle region and shows a negative correlation with the chondroitin sulfate content; in the middle part this correlation tends to become positive. 7. (7) The results are interpreted in relation to the structural and histochemical aspects of the cartilage layers; the significance of the observed heterogeneity of the chondroitin sulfate fraction and its possible relationship to differences in metabolism are discussed.