ENHANCED SUPEROXIDE ANION GENERATION BUT REDUCED LEUKOTRIENE B4 PRODUCTIVITY IN THIOGLYCOLLATE-ELICITED PERITONEAL-MACROPHAGES

Lipoxygenase metabolism of arachidonic acid was compared between peritoneal macrophages from untreated rats and those from rats on day 7 after intraperitoneal injection of thioglycollate broth (TG). Resident macrophages (Mø) from untreated rats produced mainly LTB4 ( 303 ± 25 pmol 5 × 106 cells) and 5-HETE ( 431 ± 56 pmol 5 × 106 cells) when stimulated with 5 μg/ml calcium ionophore A23187 for 20 min at 37°C. On the other hand, TG-elicited Mø generated less amounts of lipoxygenase metabolites ( 157 ± 10 pmol LTB4 and 319 ± 19 pmol 5-HETE 5 × 106 cells) with the same stimulus. Then, leukotriene productivity was examined by using subcellular fractions of each Mø lysate and an unstable epoxide intermediate, leukotriene A4. LTA4 hydrolase activity was mainly contained in soluble fractions from the both groups of Mø. The cytosol fraction from the resident Mø exhibited the following specific and total activity; 2.2 ± 0.1 nmol LTB4/mg protein/5 min and 12.2 ± 0.5 nmol LTB4/5 min per 108 cells. On the contrary, the cytosol fraction from the TG-elicited Mø showed 1.9 ± 0.1 nmol LTB4/mg protein/5 min and 9.6 ± 0.3 nmol LTB4/5 min per 108 cells. The resident Mø, however, generated 0.14 ± 0.04 nmol O2-/min/4 × 105 cells whereas the TG-elicited Mø did 0.49 ± 0.13 nmol O2-/min/4 × 105 cells when stimulated with wheat germ lectin. These results suggest that the TG-elicited macrophages show enhanced superoxide production but generate less lipoxygenase metabolites. Furthermore, reduced LTB4 productivity in the TG- elicited Mø may be attributed to a combination of less LTA4 production and also reduced LTA4 hydrolase activity in comparison with the resident Mø. © 1990.