The formation of fibrils from collagen solutions. 3. Effect of chondroitin sulphate and some other naturally occurring polyanions on the rate of formation

Abstract

Low concentrations of heparin and deoxyribonucleic acid retard fibril formation in solutions of acid-soluble collagen at pH 7, I 0.23 and 25[degree]. Two types of chondroitin sulfate (A and C) and a preparation rich in keratosulfate accelerated fibril formation. Another type of chondroitin sulfate (B) and hyaluronic acid had no effect. Those polyanions which accelerated precipitation reduced fibril width and those which retarded precipitation increased it. The accelerating effect of chondroitin sulfate A increased with decreasing pH in the range pH 6-8 and with increasing I in the range 0.13-0.31. Chondroitin sulfate A accelerated precipitation only when present during the lag period. This observation supports the conclusion from earlier work that collagen fibrils form as the result of 2 consecutive processes, nucleation and growth, and it is concluded that chondroitin sulfate A accelerates precipitation by affecting nucleation. Only a very small proportion of the added chondroitin sulfate was incorporated into the collagen precipitate. When collagen solutions were pretreated with phosphate buffer, pH 7, at 0[degree] addition of chondroitin sulfate A retarded subsequent precipitation at 25[degree], indicating that nucleation had taken place during pretreatment and that the observed retardation was due to the effect of chondroitin sulfate A on growth. The mode of action of the polyanions is considered in the light of the two-step mechanism of fibril formation and the findings are discussed in relation to the possible role of mucopolysaccharides in the formation of collagen fibrils in vivo.