HPLC analysis of oxygenated lipids present in the cellular membranes of human eosinophilic granulocytes. After preparation (see Materials and Methods), human eosinophils were incubated for 10 minutes in the absence and presence of 4 μmol/L calcium ionophore (extracellular calcium concentration of 2 mmol/L). The cells were spun down, the membrane lipids were extracted, and the extracts were hydrolyzed under alkaline conditions. HPLC analysis of the resulting free fatty acid derivatives was performed as described in the Materials and Methods section. Inset: enantiomer composition of 15-HETE isolated from the membrane lipids determined by CP-HPLC.