The determination of urinary 3-trans-hydroxyproline (3 OHP). II. Normal values in neonates, infants and preschool children.

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 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 neonates, infants and preschool children. Neonates (n = 23) showed mean excretion of 0.363 micrograms/mg creatinine (SD +/- 0.127), SEM 0.026, min. 0.197, max. 0.598. Infants (n = 11) showed mean excretion of 1.501 micrograms/mg creatinine (SD +/- 0.468), SEM 0.141, min. 0.908, max. 2.553. Preschool children (n = 16) had a mean excretion of 1.442 micrograms/mg creatinine (SD +/- 0.637), SEM 0.159, min. 0.318, max. 2.342. As determined by statistical calculations, neonates differed from infants and preschool children significantly (p less than 0.0005). Infants did not differ from preschool children, however (p less than 0.4). The reason for the low urinary excretion of 3 OHP in the neonatal period could be explained by the low enzyme activities which are physiologically observed in this developmental period in general and in the special case of a presumably low activity of the 3-prolyl-hydroxylase. Infants and preschool children presented levels 5 times higher than their neonatal mates, probably reflecting the increased 3-prolyl-hydroxylase activity which in turn is a marker of collagen synthesis.