SYNTHETIC PEPTIDE-BASED IMMUNOASSAY FOR AMINO-TERMINAL PROPEPTIDE OF TYPE-I PROCOLLAGEN - APPLICATION FOR EVALUATION OF BONE-FORMATION

Serum biochemical markers are powerful tools for the evaluation of bon e turnover. In this study, we developed a radioimmunoassay, using a sy nthetic peptide for the N-terminal fragment of human type I [alpha1(I) ] procollagen (N-PCP). A 14-amino acid peptide was synthesized from th e amino terminus and used to generate antibodies in rabbits. The synth etic peptide was used as standard and tracer in the assay. Both native type I amino procollagen (PINP), which was purified from skin fibrobl asts, and human serum displaced tracer binding in parallel with the sy nthetic peptide. The range for measurement of N-PCP in serum was 0.7 t o 30 mug/L (0.21-9.18 nmol/L). In a sample of 17 normal adults and 13 children (ages 9-16 years) there was a strong correlation between seru m N-PCP determined by this assay and both skeletal alkaline phosphatas e isoenzyme and osteocalcin, markers of bone formation. Serum concentr ations of N-PCP in a group of normal children were eightfold higher th an concentrations in normal adults, with no overlap between the two gr oups. N-PCP also correlated with C-terminal type I procollagen determi ned with a commercially available kit (r = 0.92).