Urinary excretion of D-serine in human: comparison of different ages and species.
The urinary excretion of D-serine (D-Ser) in human, rat and dog of various ages was studied. Great amounts of D-Ser were consistently excreted in human urine throughout life. No age-dependent changes were observed in urinary D-Ser/total-Ser ratios from the newborn to the aged. D-Ser/creatinine ratios in adult human urine were found to be relatively constant in individuals. The constant excretion of D-Ser in human urine was confirmed by analyzing the consecutive 24 h urine of three volunteers. High concentrations of D-Ser and D-alanine (D-Ala) were found in adult dog urine. The urinary D-Ser concentration was high in young rats at unweaned and weaned periods, and then declined with increasing age. In contrast, the urinary D-Ala concentration was very low in suckling rats, and increased rapidly after the weaned state and then declined with increasing age. The species- and age-related excretion of D-Ser in mammalian urine is considered to be due to the differences in the renal handing of D-Ser, because plasma D-Ser concentrations among the groups were not so different. Although free D-Ser has been detected in animal foods and human colostrum, the amount is insufficient to explain the concentration of D-Ser found in urine. These results indicate that urinary D-Ser in mammals may be mainly of endogenous origin.
Huang
Y
Y
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Japan.
Nishikawa
T
T
Satoh
K
K
Iwata
T
T
Fukushima
T
T
Santa
T
T
Homma
H
H
Imai
K
K
D000328:Adult; D000375:Aging / Q000652:urine*; D000409:Alanine / Q000032:analysis; D000821:Animal Feed / Q000032:analysis; D000818:Animals; D002648:Child; D002851:Chromatography, High Pressure Liquid; D003126:Colostrum / Q000737:chemistry; D004285:Dogs; D006801:Humans; D007223:Infant; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012694:Serine / Q000097:blood / Q000652:urine*
D012694:Serine; D000409:Alanine