EFFECTS OF HYPEROXIA AND NITRIC OXIDE ON ENDOGENOUS NITRIC OXIDE PRODUCTION IN POLYMORPHONUCLEAR LEUKOCYTES
T Hoehn, A Gratopp, K Raehse, P Koehne
Background and Aims:
Exposure towards hyperoxia and nitric oxide (NO)occur frequently during the treatment of neonatal hypoxic pulmonary failure. Toanalyse the response of neonatal polymorphonuclear neutrophils (PMN) tohyperoxia and NO in vitro.
Neonatal cord blood was exposed to100% oxygen, NO 20ppm plus 100% oxygen, and NO 20ppm for 30 minutes. Flowcytometry was used to quantify production of nitric oxide by measurement of theintracellular dye DAF-2 DA.
DAF-2 DA signals followingequilibration with room air were used as controls. Exposure to 100% oxygenincreased NO production significantly when compared to NO 20ppm plus 100% oxygen(p=0,031) and to NO 20ppm alone (p=0,006).
Exposure ofhuman PMN cells to hyperoxia induces intracellular upregulation of endogenousNO production, whereas exposure to exogenous NO does not. Hyperoxia - whether incombination with NO or not – can lead to NO-induced apoptosis. This needs to betaken into account in the treatment of clinical conditions requiring highinspiratory concentrations of oxygen and/or inhaled NO.