Platelet-activating factor acetylhydrolase in red cell membranes. Does decreased activity impair erythrocyte deformability in ischemic stroke patients?

BACKGROUND AND PURPOSE Platelet-activating factor acetylhydrolase hydrolyzes platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine). It also hydrolyzes oxidized derivatives of phosphatidylcholine that have a short-chain acyl residue at the sn-2 position. This enzyme may act mainly in the degradation of oxidized phospholipids and may play a role in maintaining erythrocyte deformability. Therefore, we assessed the activity of red cell membrane platelet-activating factor acetylhydrolase in patients with ischemic stroke and studied the relation of the enzyme activity to red cell deformability. METHODS Enzyme activity was measured in the detergent extract of red cell membranes from 38 patients with cerebral thrombosis and 38 age-matched healthy volunteers. Red cell filterability, an index of red cell deformability, was also measured. RESULTS The enzyme activity in patients and control subjects was 100 +/- 74 and 148 +/- 128 nmol/g protein per minute (2.68 +/- 2.11 and 3.79 +/- 2.46 pmol/10(9) cells per minute) (mean +/- SD), respectively, and the difference was significant (p < 0.05 by the Mann-Whitney U test, two-sided test). Enzyme activity was correlated positively with red cell filterability in the patients (n = 20, r = 0.565, p < 0.01). CONCLUSIONS Red blood cells from stroke patients have lower levels of platelet-activating factor acetylhydrolase activity when compared with those from healthy subjects. This may result in the accumulation of oxidized lipids in the cell membrane and lead to impaired red cell deformability in patients with cerebral thrombosis.