Abstract
Background: Homeostasis of the body osmolality is partly governed by water reabsorption through aquaporin 2 (AQP2), a vasopressin-regulated water channel of the renal collecting duct. The role of AQP2 in the development of urinary concentrating capacity during postnatal life is unknown. The aim of this study is to determine urinary excretion of AQP2 during early postnatal age at different gestational ages and during different clinical and/or biological conditions in the newborn infants.Methods: 119 premature and 6 full-term newborn infants were included in the study. Urine sample was collected at 72 hours and 3 weeks of life. Clinical and biological status was known at each sampling. No child received nephrotoxic treatment. Urinary AQP2 levels were determined by dot blot and expressed in terms of AQP/urinary creatinine.Results: 160 urine samples were analysed. Urine osmolality was low. Urinary AQP2 level increased with gestational age (p<0.05). Blood acidosis and renal impairment decreased the urinary excretion of AQP2. Prenatal glucocorticoid administration and aldosteronism (urinary Na/K ratio) increased excretion of AQP2.Conclusion: Renal concentrating capacity of the newborn is low. Nevertheless, we show that AQP2 excretion undergoes developmental changes with gestational age. In addition, different biological conditions in the neonate seems to have an impact on the level of urinary AQP2 excretion.
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