PLD activity in streptolysin O–permeabilized GTPγS-stimulated PMNs: inhibition by C₂-ceramide. PMNs were first labeled with [³H]-lyso-PAF. Incubations were carried out as described in Figure 1 except for the addition of 1% ethanol for 5 minutes at 37°C prior to the stimulation-permeabilization step. PMNs were pelleted and extracted with chloroform and methanol. TLC was performed, and the plate was exposed to film. Radioactive bands were scraped for scintillation counting. Data shown are the mean ± SEM of 5 experiments. ^*Significantly different from stimulated control; P < .001. NS indicates not significantly different from stimulated control; dpm, disintegrations per minute; and PEt, phosphatidylethanol.