Urinary angiotensinogen level is increased in preterm neonates.

Abstract

All components of the renin-angiotensin system (RAS) are abundantly synthesized in the developing kidney, suggesting that the RAS plays an important role in renal development. To examine this system in human neonates, we measured urinary angiotensinogen levels in preterm and full-term neonates and examined the relationship between urinary angiotensinogen levels and gestational age. Urine and plasma samples were collected from 20 preterm and 18 full-term neonates at birth. Angiotensinogen levels were measured using enzyme-linked immunosorbent assay. Plasma angiotensinogen concentrations were not increased in preterm neonates compared with that in full-term neonates (P = 0.7288). However, the urinary angiotensinogen-to-creatinine ratio was significantly higher in preterm neonates compared with that in full-term neonates (P = 0.0011). Importantly, the urinary angiotensinogen-to-creatinine ratio dropped significantly with increasing gestational age (P = 0.0010), whereas the plasma angiotensinogen concentration was not correlated with gestational age (P = 0.7814). These results suggest that urinary angiotensinogen levels may indicate the involvement of intrarenal RAS activation in prenatal renal development.