Nitric oxide-mediated augmentation of polymorphonuclear free radical generation after hypoxia-reoxygenation.
Polymorphonuclear leukocytes (PMNLs), nitric oxide (NO), calcium, and free radicals play an important role in hypoxia/ischemia and reoxygenation injury. In the present study, NO donors, sodium nitroprusside (SNP), and diethylamine-NO (DEA-NO) at low concentrations (10 and 100 nmol/L) potentiated, while higher (10 micromol/L to 10 mmol/L) concentrations inhibited free radical generation response in the rat PMNLs. Free radical generation response was found to be significantly augmented when hypoxic PMNLs were reoxygenated (hypoxia-reoxygenation [H-R]). This increase in free radical generation after reoxygenation or SNP (10 nmol/L) was blocked in the absence of extracellular calcium. SNP (10 nmol/L) or H-R-mediated increases in the free radical generation were prevented by the pretreatment of PMNLs with NO scavenger (hemoglobin), the polyadenine diphosphate (ADP)-ribosylation synthase inhibitor (benzamide) or the calcium channel antagonist (felodipine). A significant augmentation in the nitrite and intracellular calcium levels was observed during hypoxia. Hemoglobin pretreatment also blocked the increase in intracellular calcium levels due to SNP (10 nmol/L) or hypoxia. Thus, increased availability of NO during SNP treatment or H-R, may have led to an ADP-ribosylation-mediated increase in intracellular calcium, thereby increasing the free radical generation from the rat PMNLs.
Sethi
S
S
Pharmacology Division, Central Drug Research Institute, Lucknow, India.
Singh
M P
MP
Dikshit
M
M
D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D001549:Benzamides / Q000494:pharmacology; D015687:Cell Hypoxia / Q000502:physiology; D015736:Felodipine / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D006454:Hemoglobins / Q000494:pharmacology; D008163:Luminescent Measurements; D008297:Male; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009599:Nitroprusside / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism
D001549:Benzamides; D005609:Free Radicals; D006454:Hemoglobins; D020030:Nitric Oxide Donors; D017382:Reactive Oxygen Species; D009599:Nitroprusside; D016718:Arachidonic Acid; D009569:Nitric Oxide; C037689:benzamide; D019001:Nitric Oxide Synthase; D015736:Felodipine; D010100:Oxygen