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[Molecular weight analysis of physiological proteinuria in newborn infants (author's transl)]
Insights
Newborn infants show temporary kidney immaturity, with altered urinary protein excretion patterns in the first week of life. These patterns normalize as kidney function matures, particularly tubular reabsorption.
Area of Science:
- Nephrology
- Biochemistry
- Pediatrics
Context:
- Neonatal kidney function differs significantly from that of older children.
- Urinary protein excretion patterns reflect the maturity of renal filtration and reabsorption.
- Understanding these changes is crucial for assessing neonatal kidney health.
Purpose:
- To analyze and compare urinary protein and glycoprotein excretion in newborns versus older children.
- To identify specific protein fractions that change in excretion during the first week of life.
- To correlate urinary protein profiles with renal immaturity in neonates.
Summary:
- Newborns exhibit higher proportions of low and high molecular weight proteins, and albumin in initial urine samples.
- Within one week, low molecular weight proteins become predominant due to decreased albumin and high molecular weight protein excretion.
- Urinary protein excretion patterns in newborns differ from older children, indicating transient renal immaturity.
Impact:
- Highlights the temporary immaturity of the glomerular filter and tubular reabsorption in newborn kidneys.
- Suggests that tubular protein handling normalizes later than glomerular protein filtration.
- Provides insights into the developmental trajectory of neonatal renal physiology.
Abstract:
The physiological protien and glycoprotein excretions in the urine samples of a larger group of newborn infants were separated according to the molecular weights by SDS polyacrylamide gel electrophoresis and compared with the protein excretions of older children. We found higher proportions of albumin, of high molecular weight (MW = molecular weight greater than or equal to 150 000 dt) and of lower molecular weight (MW less than albumin 6800 dt) proteins in the first 24-h urine samples after birth. One week after birth the low molecular weight proteins predominated because there was a substantial decrease in the excretion of albumin and of high molecular weight proteins (MW greater than or equal to 150 000 dt). We compared the patterns of protein excretion of the newborn infants with those of children aged from 2 1/2 to 15 years. These urines samples showed a typical pattern of protein excretion not correlated to the age. These findings express a transitory immaturity of the glomerular filter and of the tubular protein reabsorbing system of the newborn kidney. Apparently, the tubular protein handling normalizes later than the glomerular filtration of proteins.