Blood-induced superoxide anion generation on the cerebral cortex of newborn pigs

Pigs were equipped with closed cranial windows to measure superoxide anion generation in response to blood placed on the cerebral cortex. Superoxide dismutase (SOD)-inhibitable nitro blue tetrazolium (NBT) reduction was measured in the presence of 1) artificial cerebrospinal fluid (CSF), 2) homologous nonheparinized blood (blood), and 3) blood after treatment with indomethacin. SOD-inhibitable NBT reduction was increased significantly in the blood group compared with control, whereas piglets pretreated with indomethacin had significantly less SOD-inhibitable NBT reduction. This suggests that superoxide anion is generated by extravascular blood and that this superoxide anion generation can be inhibited by indomethacin. To investigate the cellular origin of superoxide anion generation, SOD-inhibitable NBT reduction was measured during incubation with piglet whole blood or its components in vitro. The SOD-inhibitable NBT reduction of nonheparinized whole blood was 30 +/- 5.7 nmol.ml-1.20 min-1. This decreased to 2.5 +/- 1.3 nmol.ml-1.20 min-1 in the presence of indomethacin. SOD-inhibitable NBT reduction of ADP-stimulated platelet-rich plasma was 25.6 +/- 2.9 nmol.400 X 10(6) cells-1.20 min-1 and was decreased significantly (6.8 +/- 3.0 nmol.400 X 10(6) cells-1.20 min-1) in the presence of indomethacin. SOD-inhibitable NBT reduction by granulocytes was significant but unchanged by indomethacin. Similarly, SOD-inhibitable NBT reduction by lymphocytes and monocytes was unaffected by indomethacin. Reduction by the red cell fraction was small. These results suggest that substantial quantities of superoxide anion are generated via the platelet cyclooxygenase pathway of arachidonic acid metabolism.