Urinary excretion of aquaporin-2 in term and preterm infants

Aquaporin-2 (AQP-2) is a vasopressin-regulated water channel of the renal collecting duct and is excreted in human urine. We measured the urinary excretion of AQP-2 by radioimmunoassay in 14 term and 12 preterm infants aged 1 month. Excretion of AQP-2 was low compared with adults, and correlated significantly with urine osmolality in preterm infants. Our results demonstrate that AQP-2 water channels are expressed in the renal collecting duct of both term and preterm infants.