The periphery of the developing collagen fibril. Quantitative relationships with dermatan sulphate and other surface-associated species

Abstract

Dermatan sulfate, hydroxyproline and collagen fibril diameters were measured in flexor tendons from chick and calf limbs, from early in embryonic development to maturity. The collagen fibril is viewed as a long thin cylinder. A species X present at the periphery of the cylinder, regularly and specifically arrayed along the fibril, should then satisfy the relationship [X]/[collagen]r = k where [X] and [collagen] are tissue concentrations of X and collagen, and r is the fibril radius. Throughout the developmental period studied, dermatan sulfate (i.e., X) in chick, calf and rat tendons fits the relationship, implying that it is specifically, regularly and entirely associated with collagen fibrils; this confirms and extends previous electron histochemistry. This approach explains the pattern of change of dermatan sulfate content during development of the tendon. The dermatan sulfate proteoglycan-collagen interaction is evolutionally highly conserved. The relationship [X]/[collagen]r = k is used to show that surface concentrations of covalently bound species, such as extension propeptides, can be easily assessed, given the data base described.