Acetyl-CoA:lyso-Platelet-Activating Factor Acetyltransferase Activity in Neutrophils from Asthmatic Patients and Normal Subjects

Abstract

1. Platelet-activating factor is a putative mediator of inflammation in asthma and the enzyme acetyl-CoA:lyso-platelet-activating factor acetyltransferase appears to be important in regulating platelet-activating factor production by leucocytes. To determine whether there are differences in acetyltransferase activity between asthmatic patients and normal subjects, enzyme activity was assayed in neutrophil lysates from atopic asthmatic patients (n = 20), aspirin-sensitive asthmatic patients (n = 12) and healthy, non-atopic, non-asthmatic control subjects (n = 20), both basally and after stimulation with the calcium ionophore A23187. 2. For a range of acetyl-CoA concentrations, acetyltransferase activity (nmol of [acetyl-3H]PAF min-1 mg-1 of protein) in unstimulated neutrophils from atopic asthmatic patients was significantly higher than that for normal subjects (P = 0.038) and the mean Vmax. for atopic asthmatic patients [18.4 (SD 6.9) nmol min-1 mg-1 of protein] was significantly greater than that for the control subjects [14.9 (SD 4.6) nmol min-1 mg-1 of protein P < 0.05]. The mean Vmax. for aspirin-sensitive asthmatic patients [15.9 (SD 6.9) nmol min-1 mg-1 of protein] was not significantly different from that for the normal subjects. 3. The mean ratio Vmax. stimulated/Vmax. unstimulated for acetyltransferase from atopic asthmatic patients (1.71, SD 0.45) was significantly less than that for the normal subjects (2.13, SD 0.63, P < 0.05), suggesting that acetyltransferase from atopic asthmatic patients was less sensitive to stimulation with A23187 in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)