The determination of urinary 3-trans-hydroxyproline (3 OHP). I. Normal values in school children and adults

3-trans-hydroxyproline is a hydroxyproline isomer present in collagens. It is more abundant in basement membrane collagen (collagen type IV) where it can be found in a relation of 12 residues per 1000 amino acid residues. This implicates its probable use as a marker substance for collagen type IV metabolism. Up to now only hydrolyzed urine samples were examined for the presence of this amino acid, thus indicating total urinary excretion. We are reporting the free urinary 3 OHP content of adults and school children. School children (age group 8-18 years) showed mean excretion of 1.066 micrograms/mg creatinine (SD +/- 0.376), SEM 0.054, min. 0.516; max. 2.397, range: 1.881. Adults (age 19-29 years) showed mean excretion of 0.618 micrograms/ml creatinine (SD +/- 0.465), SEM 0.134, min. 0.055; max. 1.634, range: 1.579. As given by the statistical calculation of unpaired t-test, adults showed significantly lower urinary 3 OHP levels: t = 3.518 and p = less than 0.0005. This can be explained by increased collagen metabolism of the growing organism and is in congruence with data reported in literature for total urinary 3 OHP excretion.