Blood cardiolipin in haemodialysis patients. Its implication in the biological action of platelet-activating factor.

Bovine heart cardiolipin specifically inhibits platelet aggregation induced by PAF in vitro. In the past we have reported that patients with primary glomerulonephritis have increased PAF levels in plasma (Iatrou et al., 1995b). In this work we investigate the existence of cardiolipin in the blood of end-stage renal patients due to primary glomerulonephritis and we study its implication in the biological study of PAF. Lipids from blood samples of end-stage renal patients were extracted, fractionated onto silicic acid column and onto High Performance Liquid Chromatography (HPLC) cation exchange column. PAF fraction was removed and phospholipids were separated from the rest lipid fraction with current counter distribution and furthermore fractionated onto HPLC silica column. The results show: 1. cardiolipin is present in the blood of end-stage renal patients. 2. Blood cardiolipin specifically inhibits PAF-induced aggregation in washed rabbit platelets. 3. Scatchard plot analysis of PAF binding, in the presence of unlabelled PAF and in the presence of cardiolipin, shows that rabbit platelets possess two different types of binding sites. One of which is saturable and of high affinity, kD = 0.103 +/- 0.03 nM (SEM, n = 3) with 337 +/- 94 binding sites per platelet for PAF and kD = 0.087 +/- 0.02 nM with 371 +/- 92.7 binding sites per platelet for cardiolipin while the other one has almost infinite binding capacity. 4. Blood cardiolipin competes [3H]PAF binding in rabbit platelets. This work shows that cardiolipin exists in the blood of end-stage renal patients and specifically inhibits PAF-induced aggregation as well as PAF binding in rabbit platelets. The possible implication of the biological actions of cardiolipin in the anticardiolipin-antiphospholipid syndrome is also discussed.