SERUM CONTENT OF THE C-PROPEPTIDE OF THE CARTILAGE MOLECULE TYPE-II COLLAGEN IN CHILDREN

Objective. The C-propeptide of cartilage type II procollagen, together with the N-propeptide, are removed from newly synthesized procollagen during collagen fibril assembly in cartilage matrix. The presence and content of the C-propeptide reflect the synthesis of this molecule. R ecently, we showed that serum levels of the C-propeptide are increased in adults with rheumatoid arthritis, pointing to increased synthesis of this molecule. In this study we examined its content in the sera of children to determine whether it changes during development. Methods. Sera were obtained from 44 premature infants (cord blood), 75 childre n (0-18 years), 14 young adults (18-22 years) and 47 adults (35-60 yea ts). The concentration of serum C-propeptide of type TI procollagen wa s determined by a solution phase competitive inhibition radioimmunoass ay which uses a polyclonal antiserum specific for the bovine and human C-propeptide. Results. Compared with adults, concentrations of the C- propeptide of type II procollagen were significantly elevated in child ren of ages 0-14 years. Concentrations were constant until 10 years of age (premature infants: 14.5 +/- 1.4 ng/ml, mean +/- SE; 0-10 years: 13.6 +/- 1 ng/ml), In children of ages 10-14 years, during which the p ubertal growth spurt is ordinarily observed, the mean concentration in creased (10-14 years: 21.6 +/- 0.7 ng/ml) although not significantly d ue to the variation between individuals. Concentrations at all ages yo unger than 14 were significantly greater than those in older adolescen ts ages 14-18 (6.3 +/- 0.7 ng/ml), young adults (8.4 +/- 2.0 ng/ml) an d adults (5.7 +/- 0.4 ng/ml). Serum concentrations did not show signif icant differences with respect to sex, but varied from child to child at any given age. Conclusions. The measurement of this circulating C-p ropeptide may be of use in studying the biochemical and physiological bases of changes in cartilage turnover in children, and abnormalities thereof.