Biochemical analysis of normal articular cartilage in horses

Anne M. Vachon From the Departments of Clinical Sciences (Vachon, Mcllwraith) and Statistical Sciences (Chapman), College of Veterinary Medicine, Colorado State University, Fort Collins, Col 80523, and the Research Institute of The Hospital for Sick Children Toronto, Canada MG5 1X8 (Keeley).

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Fred W. Keeley From the Departments of Clinical Sciences (Vachon, Mcllwraith) and Statistical Sciences (Chapman), College of Veterinary Medicine, Colorado State University, Fort Collins, Col 80523, and the Research Institute of The Hospital for Sick Children Toronto, Canada MG5 1X8 (Keeley).

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C. Wayne McIlwraith From the Departments of Clinical Sciences (Vachon, Mcllwraith) and Statistical Sciences (Chapman), College of Veterinary Medicine, Colorado State University, Fort Collins, Col 80523, and the Research Institute of The Hospital for Sick Children Toronto, Canada MG5 1X8 (Keeley).

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Phillip Chapman From the Departments of Clinical Sciences (Vachon, Mcllwraith) and Statistical Sciences (Chapman), College of Veterinary Medicine, Colorado State University, Fort Collins, Col 80523, and the Research Institute of The Hospital for Sick Children Toronto, Canada MG5 1X8 (Keeley).

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SUMMARY

Articular cartilage specimens from the distal articular surface of 32 radiocarpal bones from 24 2- to 5-year-old horses were analyzed. The total collagen content was determined on the basis of the 4-hydroxyproline content, using a colorimetric method. A method for estimating the proportions of types-I and -II collagen by measuring spectrophotometric densities of specific cyanogen bromide peptide bands from mixtures of types-I and -II collagen on sodium dodecyl sulfate-polyacrylamide gels was used. The cyanogen bromide peptides representative of each collagen types-I and -II were identified. The peptide ratios were then computed for each of several standards of type-I and -II mixtures. A standard curve was derived from the correlation between these ratios and the corresponding proportions of type-II collagen in standard mixtures. Galactosamine and glucosamine content (hexosamines) were measured by ion chromatography. The galactosamine-to-glucosamine ratio, chondroitin sulfate and keratan sulfate values, and total glycosaminoglycan content were derived from the measured hexosamine content.

The total collagen content averaged 556 mg/g (55.6 mg/100 mg) of tissue (dry weight, [dw]). Type-II collagen was the major collagen type in normal articular cartilage specimens. The ratio of the area under the αl (II)CBIO peak to the area under the αl (I)CB 7,8 + αl (II)CB11 peak was a second-order polynomial function of the proportion of type-II collagen in the specimens. The mean galactosamine and glucosamine content were 20.6 mg/g and 7.9 mg/g (dw), respectively. The mean galactosamine-to-glucosamine ratio was 3.74 ± 0.62. Chondroitin sulfate values, keratan sulfate values, and total glycosaminoglycan content were 53.3 ± 4.9 mg/g, 19.9 ± 3.6 mg/g, and 73.2 ± 7.9 mg/g (dw), respectively. There was no significant correlation between the age of the horses and any of the chemical values (P > 0.1). The biochemical composition of articular cartilage in the horse is similar to that of other species.

SUMMARY

Articular cartilage specimens from the distal articular surface of 32 radiocarpal bones from 24 2- to 5-year-old horses were analyzed. The total collagen content was determined on the basis of the 4-hydroxyproline content, using a colorimetric method. A method for estimating the proportions of types-I and -II collagen by measuring spectrophotometric densities of specific cyanogen bromide peptide bands from mixtures of types-I and -II collagen on sodium dodecyl sulfate-polyacrylamide gels was used. The cyanogen bromide peptides representative of each collagen types-I and -II were identified. The peptide ratios were then computed for each of several standards of type-I and -II mixtures. A standard curve was derived from the correlation between these ratios and the corresponding proportions of type-II collagen in standard mixtures. Galactosamine and glucosamine content (hexosamines) were measured by ion chromatography. The galactosamine-to-glucosamine ratio, chondroitin sulfate and keratan sulfate values, and total glycosaminoglycan content were derived from the measured hexosamine content.

The total collagen content averaged 556 mg/g (55.6 mg/100 mg) of tissue (dry weight, [dw]). Type-II collagen was the major collagen type in normal articular cartilage specimens. The ratio of the area under the αl (II)CBIO peak to the area under the αl (I)CB 7,8 + αl (II)CB11 peak was a second-order polynomial function of the proportion of type-II collagen in the specimens. The mean galactosamine and glucosamine content were 20.6 mg/g and 7.9 mg/g (dw), respectively. The mean galactosamine-to-glucosamine ratio was 3.74 ± 0.62. Chondroitin sulfate values, keratan sulfate values, and total glycosaminoglycan content were 53.3 ± 4.9 mg/g, 19.9 ± 3.6 mg/g, and 73.2 ± 7.9 mg/g (dw), respectively. There was no significant correlation between the age of the horses and any of the chemical values (P > 0.1). The biochemical composition of articular cartilage in the horse is similar to that of other species.

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