Relationship between platelet phospholipase activity and plasma in ischemic heart disease

Serum phospholipase A2 and lysolecithin changes following myocardial infarction

We have examined changes in the activities of phospholipase A2 (PLA2) and the concentrations of total choline-phospholipids and lysolecithin, in serum from patients following a myocardial infarction by comparison with patients suffering from unstable angina. A significant increase in PLA2 activity was found after myocardial infarction. The peak increase occurred approximately 36 h after infarction. No significant PLA2 change was found in the patients with unstable angina. Concentrations of lysolecithin, the major metabolite of PLA2 activity, were high in the admission samples from the infarction patients, followed by an overall fall during the first 24 h: the concentrations in the patients with angina were normal. PLA2 and lysolecithin changes post-infarction showed they were involved in processes not occurring in angina.

Plasma phospholipase A2 activity in clinical acute myocardial infarction

1. Phospholipase A2 (PLA2) cleaves phospholipids to produce a lyso-phospholipid and free fatty acid and, in view of the biological activity of the products, PLA2 may play a role in many disease states. Lyso-phospholipids and free arachidonic acid increase in ischaemic myocardium, indicating that ischaemia activates the enzyme. 2. Plasma PLA2 activity was measured in patients with acute myocardial infarction, based on the release of labelled arachidonic acid from Escherichia coli cell membrane. Fourteen males (peak serum creatine phosphokinase (CK) above twice upper normal) were studied on day 1 (within 6 h of chest pain onset), days 2-4, and days 6-9. Normal age matched males (n = 13) were also studied. 3. Plasma PLA2 in patients with uncomplicated myocardial infarction (n = 12) was, initially, 1.14 +/- 0.10 (s.e.m.) nmol/min per mL plasma, similar to that in the normal group (1.52 +/- 0.14). On days 2-4, PLA2 activity increased to 1.94 +/- 0.18 (P less than 0.001) and this activity was correlated with the earlier peak CK level (P less than 0.02). On days 6-9, PLA2 activity was 1.49 +/- 0.13 while in two patients who developed complications and underwent open-heart surgery between the last two measurements, there were further increases to 4.22 and 4.04 nmol/min per mL. 4. The increase in plasma PLA2 in uncomplicated myocardial infarction is likely to be due to release from the damaged myocardium; whether it contributes to pathophysiology is uncertain.

Lipolytic enzyme and phospholipid level changes in intraoperative salvaged blood

Autotransfusion is becoming increasingly popular, mainly because it eliminates the risk of disease transmission. One of the techniques available is intra-operative blood salvage and retransfusion with or without washing of the collected blood. The blood collected during this process is subjected to a variety of chemical and physical insults which can alter the normal composition of the plasma by activating plasma and cellular homeostatic mechanisms. In this study, we measured the plasma levels of total phospholipids, lysolecithin and non-esterified fatty acids, and the lipolytic enzymes phospholipase A2 (PLA2) and lipase in the salvaged blood before and after washing. In the unwashed salvaged blood the mean levels of PLA2, non-esterified fatty acids and lysophospholipids increased by 144, 96 and 149%, respectively, while those of total phospholipids and lipase did not change to any extent. All these substances were reduced to well below the patients circulating plasma levels by washing the collected blood. The changes indicate that the lipid profile of salvaged blood is significantly altered and that potentially dangerous substances such as PLA2 and its metabolites, lysolecithin and non-esterified fatty acids, are present in increased amounts. Washing the blood is recommended prior to reinfusion.