Plasma levels of L-citrulline (A), L-arginine (B), ornithine (C) and NOx (D) were measured on P7, 10 and 14 (N=5/group, *P<0.05 and **P<0.0005, normoxia vs hyperoxia, §P<0.001, normoxia (■) and hyperoxia (◆) vs normoxia+L-Citrulline (⨯) and hyperoxia+L-Citrulline (▲). Inset shows plasma levels of L-Citrulline in normoxia (■) and hyperoxia (◆) only