Renal PGE2 in preterm infants: a possible role in the adaptation to extrauterine life

Background: Prostanoids contribute to important changes during transition from fetal to newborn life. In particular, PGE2 play a crucial role in protecting the immature kidney from high levels of angiotensin II. Aim: To measure urinary PGE2 excretion in preterm neonates of different G.A. at birth, since there is evidence that PGE2 concentrations in urine reflect predominantly their renal generation and then could be correlated with kidney maturation or renal problems. Methods: Thirty-eight preterm infants admitted to the neonatal intensive care unit at the University of Cagliari, Italy, were divided in three groups according to their G.A.: Group A (n=9, mean G.A. 27.6+1.7 wks, mean B.W. 1013+340 g); Group B (n=19, mean G.A. 30.8+0.8 wks, mean B.W. 1529+468 g); Group C (n=10, mean G.A. 34.4+1.3 wks, mean B.W. 2056+515 g). None of the neonates had been asphyxiated at birth and none had a specific renal abnormality or other clinical conditions influencing renal function. Spot urine samples, collected on days 2-3 of life, were analyzed for PGE2 using a commercially available kit (Cayman Chem, Ann Arbor, MI, USA). Results: By comparing PGE2 concentrations among the three groups with ANOVA test (Group A: 65.67+12.97 pg/ml; Group B: 77.84+11.46 pg/ml; Group C: 51.90+11.49 pg/ml), a statistically significant difference was observed (F=16.01, p<0.001). Moreover, in neonates of groups A and B with a G.A. <33 weeks, a positive linear correlation was found between PGE2 values and G.A. (r=0.53, p=0.003). Conclusions: From our data, the higher PGE2 values observed in neonates where nephrogenesis was not completed (G.A. <33 wks) could be due to an altered passive reabsorption of PGE2 along the nephron because of kidney immaturity or could reflect a mechanism of protection for these neonates at higher risk to develop renal problems.