NITRIC-OXIDE SYNTHASE INHIBITION DECREASES TOLERANCE TO HYPEROXIA IN NEWBORN RATS

WE evaluated the effects of sustained perinatal inhibition of NO synth ase (NOS) on hyperoxia induced lung injury in newborn rats. N-G-nitro- L-arginine-methyl-ester (L-NAME) or untreated water was administered t o pregnant rats for the final 7 days of gestation and during lactation ; followed by postnatal exposure to hyperoxia (>95% O-2) or room air. The survival rate of L-NAME treated pups when placed in >95% O-2 at bi rth was significantly lower than controls from day 4 (L-NAME, 87%; con trol pups, 100%, p < 0.05) to 14 (L-NAME, 0%; control pups, 53%, p < 0 .05). Foetal pulmonary artery vasoconstriction was induced by L-NAME w ith a decrease in internal diameter from 0.88 +/- 0.03 mm to 0.64 +/- 0.01 mm in control vs. L-NAME groups (p < 0.05), respectively. We conc lude that perinatal NOS inhibition results in pulmonary artery vasocon striction and a decreased tolerance to hyperoxia induced lung injury i n newborn rats.