Neutrophil Adhesion Molecule Expression in the Developing Neonatal Rat Exposed to Hyperoxia

Neonatal rats have an increased tolerance to hyperoxia, which is associated with a diminished pulmonary inflammatory response compared with adults. To investigate this differing response, expression of the neutrophil adhesion molecules, L-selectin and CD18, and levels of soluble L-selectin, were examined using flow cytometry and sandwich enzyme-linked immunosorbent assay on air-exposed neonatal rat neutrophils at 0–24 and 72 h and 7, 10, 14, and 21 d of age compared with the adult and after exposure to hyperoxia (⩾ 98% O2) for 56 h in adults and for 72 h and 7 d in neonates. Expression of L-selectin in 0–24-h neonates was similar to adults, but was significantly lower than adults at 72 h and 7 d (P = 0.011). Soluble L-selectin levels were significantly higher than those in adults in the 0–24- and 72-h neonates (P < 0.001). CD18 expression in unstimulated and activated neutrophils of neonatal rats was higher at 0–24 h than in the adult (P < 0.001), but thereafter did not differ from adults. After hyperoxic...