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Creatinine reabsorption by the newborn rabbit kidney
P Matos1, M Duarte-Silva, A Drukker
1Department of Pediatrics, University Medical Center, Lausanne, Switzerland.
Pediatric Research
|November 6, 1998
Summary
Neonatal kidneys reabsorb creatinine, unlike adult kidneys which secrete it. This tubular reabsorption in newborns, particularly premature infants, contributes to elevated plasma creatinine levels post-birth.
Area of Science:
- Nephrology
- Neonatal Physiology
- Renal Function
Background:
- Plasma creatinine levels are elevated in newborns, especially premature infants, beyond maternal transfer levels.
- The renal handling of creatinine by immature kidneys requires further definition.
Purpose of the Study:
- To investigate the renal handling of creatinine in neonatal rabbits compared to adults.
- To determine if tubular secretion or reabsorption of creatinine occurs in immature kidneys.
Main Methods:
- Simultaneous measurement of creatinine and inulin clearances in adult and neonatal rabbits.
- Exogenous creatinine infusion in neonatal groups to achieve specific plasma creatinine concentrations.
Main Results:
- Adult rabbits showed creatinine clearance > inulin clearance (ratio 1.21), indicating tubular secretion.
- Neonatal rabbits with adult-like plasma creatinine levels exhibited a creatinine/inulin clearance ratio < 1 (0.84), suggesting reabsorption.
- Neonatal rabbits with doubled plasma creatinine levels showed a ratio near 1 (0.96).
Conclusions:
- Newborn rabbits reabsorb creatinine along the tubule.
- Immature, "leaky" tubules likely facilitate creatinine back-leak, explaining elevated postnatal plasma creatinine levels.