Respiratory burst activity in brain macrophages: a flow cytometric study on cultured rat microglia

A new flow cytometric method for the investigation of the respiratory burst of macrophages/microglia isolated from neonatal rat brain has been established. Respiratory burst activity was measured quantitatively in single viable cells by the intracellular oxidation of non-fluorescent dihydrorhodamine 123 (DHR) to fluorescent rhodamine 123. Cultured microglia exhibited high spontaneous respiratory burst activity already before stimulation. After maximal stimulation with phorbol myristate acetate, DHR oxidation rose by 40-95%. The respiratory burst activity in resident or inflammatory, i.e. thioglycolate elicited, peritoneal macrophages was significantly lower than in cultured brain macrophages suggesting a high potential of microglia for oxidative tissue destruction.