Suppression of lysophosphatidic acid and lysophosphatidylcholine formation in the plasma in vitro: Proposal of a plasma sample preparation method for laboratory testing of these lipids

It is now established that lysophosphatidic acid (LPA) and lysophosphatidylcholine (LPC) play important roles in a variety of biological responses, especially in the area of vascular biology, and determination of their concentrations in the plasma is believed to be clinically relevant. Preparation of the measurement samples is a difficult task, however, because the blood levels of these lipids can be easily increased by in vitro manipulation after venepuncture. In this study, we examined the optimal conditions for the preparation of plasma samples for the measurement of LPA and LPC. It appears that regulation of platelet activation and the enzymatic activity of lysophospholipase D/autotaxin and lecithin–cholesterol acyltransferase is important to suppress the undesirable formation of LPA and LPC after venepuncture. We found that in vitro formation of LPA and LPC was negligible when whole blood samples were mixed with 7.5 mM EDTA plus 10% (v/v) citrate–theophylline–adenosine–dipyridamole (CTAD) and when all of the procedures, including the plasma preparation and preservation until measurement, were performed at 4 °C. Thus, although the plasma levels of LPA and LPC can be easily altered, laboratory testing of these important bioactive lipids for clinical purposes may be conducted reliably if the samples are prepared under stringent conditions.