Excretion Of Free Hydroxyproline Research Articles

Connective tissue metabolism in children with chronic renal failure.

To assess the characteristics of connective tissue metabolism in chronic renal failure (CRF), urinary excretion of glycosaminoglycan (GAG) fractions and hydroxyproline (HYP) was determined in ten patients with CRF and in ten age-matched healthy children. CRF was found to be associated with elevated free HYP (19.9 +/- 6.1 vs 9.8 +/- 3.6 mumol/day, P less than 0.05) and depressed peptide HYP excretion (33.1 +/- 13.5 vs 225.2 +/- 17.7 mumol/day, P less than 0.01), a low rate of total GAG excretion (7.0 +/- 2.4 vs 16.1 +/- 1.9 mumol uronic acid/day, P less than 0.05) with low chondroitin 4 -sulphate + chondroitin 6 -sulphate (Ch-Ss) (14.0 +/- 9.9 vs 65.0 +/- 22.1%) and a high proportion of non-sulphated or under-sulphated fractions, i.e. hyaluronic acid + chondroitin + heparan sulphate (HA + Ch + HS) (75.3 +/- 11.4 vs 31.5 +/- 5.7%). Urinary 3-methyl-histidine (3-met-HIS) excretion and plasma essential free amino acids did not differ in the two groups. In response to haemodialysis no consistent change occurred in urinary excretion of 3-met-HIS, peptide-bound HYP, total GAG or percentage distribution of individual GAG fractions. After haemodialysis all plasma amino acids decreased significantly, and there was a significant increase in urinary excretion of free HYP (P less than 0.05). We conclude that the alterations in urinary excretion of total and individual GAGs observed in CRF may reflect disturbed connective tissue metabolism which does not appear to be accounted for by protein malnutrition or enhanced protein breakdown and remains uninfluenced by haemodialysis therapy.

Hydroxyprolinemia III. The origin of free hydroxyproline in hydroxyprolinemia. Collagen turnover. Evidence for a biosynthetic pathway in man

1. 1. A patient with hydroxyproline oxidase deficiency offered a unique opportunity to investigate the origin of plasma and urine hydroxyproline, since most of the free hydroxyproline produced in this patient is accumulated in blood and excreted unchanged in the urine. Dietary origin had been ruled out previously. 2. 2. The hydroxyproline-containing peptides in the urine were not different from normal. There was no evidence of abnormal collagen breakdown. Results indicate that the free hydroxyproline derives from a normal collagen turnover of about 2 g/day. 3. 3. Trial of a scorbutic diet unexpectedly resulted in a striking increase in excretion of free and peptide-bound hydroxyproline in the urine, and a further increase in plasma hydroxyproline concentration. This is in contrast to the decreased urinary hydroxyproline observed in scorbutic guinea pigs. Administration of ascorbic acid after the period of depletion resulted in further increase in excretion of free hydroxyproline. This suggests that ascorbic acid depletion in man increases turnover of mature collagen or of partially hydroxylated collagen precursors. 4. 4. When labeled glyoxylate was administered, a significant though small amount of urinary free hydroxyproline became labeled, indicating a slight degree of biosynthesis from glyoxylate in man, as has been described in rat livers.

Catabolism and excretion of free hydroxyproline in infancy.

ABSTRACT Collagen degradation is essentially the only source of free and peptide hydroxyproline in plasma and urine. Normally over 95% of the hydroxyproline in urine is peptide-bound, and the excretion of peptide hydroxyproline has been used to follow collagen metabolism. Newborn infants 1–2 wk old excreted about 60 times more free hydroxyproline per kg than infants 6–12 months old. The excretion of hydroxyproline peptides per kg in the young infants was only slightly greater than the hydroxyproline peptide excretion in the older infants, suggesting that changes in collagen catabolism cannot be a major factor in explaining the large excretion of free hydroxyproline in young infants. In fullterm infants the ratio of free to peptide hydroxyproline in urine appeared to increase during the first few days of life, and then it gradually decreased to adult levels in about 5 months. The ratio of free to peptide hydroxyproline in urine was even higher in premature infants, and it remained high longer than in full-...

Hydroxyprolinemia and increased excretion of free hydroxyproline in early infancy.

Isotopic studies have indicated that the hydroxyproline excreted in urine is derived primarily from the degradation of collagen (1, 2), and that the excretion of hydroxyproline can be used as a measure of collagen metabolism (for reviews, see 3, 4). Normally, 95% or more of the hydroxyproline excreted in the urine of children and adults appears as peptides, and less than 5% is present as the free imino acid. No significant change in the ratio of free to peptide hydroxyproline in urine has been demonstrated in most conditions in which collagen degradation and the excretion of peptide hydroxyproline are increased (3, 4). The relatively small amounts of free hydroxyproline in urine are probably explained by the higher renal threshold for free hydroxyproline than for peptide hydroxyproline (5, 6) and by the rapid enzymatic degradation of free hydroxyproline to Δ-pyrroline-3-hydroxy-5-carboxylic acid and γ-hydroxy-l-glutamic acid (see 7). Recently, Efron et al. (7) have observed high levels of free hydroxyprol...

Urinary Excretion of Several Metabolites in Persons Accidentally Exposed to Ionizing Radiation

BS>Urinary concentrations of creatine, beta -aminoisobutyric acid, pyrrole --carboxylic acid, and free hydroxyproline were determined in human subjects accidentally exposed to ionizing radiation at various time intervals after exposure. The range of doses of radiation varied from about 100 to 4000 rads. Increased concentrations of creatine and beta -aminoisobutyric acid in urine were found in most of the patients. Excretion of free hydroxyproline was decreased in the three most heavily exposed patients, whereas pyrrolecarboxylic acid was increased only in the fatally injured patient. (auth)