Nitric oxide effects on lung structure and blood oxygen affinity in rats.

Two month-old Wistar rats were exposed continuously for six weeks, either to 2.0 +/- 0.1 ppm nitric oxide (NO) mixed homogeneously with air for tests, or to ambient air for controls. Oxyhemoglobin dissociation curve (ODC), erythrocytic variables, methemoglobin (MetHb) concentration and lung structure, particularly through electron microscopy studies, were investigated each week of exposure. The hemoglobin affinity for oxygen was not modified, probably as a result of both pH and 2,3-diphosphoglycerate (2,3-DPG) stability. Moreover MetHb formation was not found in treated rats. The few ultrastructural alterations found under electron microscopy may not prove NO-induced since they were found similarly in both groups. Slight emphysematous changes were found only in 1 micrometer-thick sections of lungs from NO-treated rats.