ROUTINE MEASUREMENT OF THROMBOXANE-B-2 AND THE PROSTACYCLIN METABOLITE 6-KETO-PROSTAGLANDIN-F-1-ALPHA IN PLASMA

Abstract

Thromboxane A2 (TXA2) is mainly formed in thrombocytes. It promotes thrombocyte aggregation and contracts the blood vessels. TXA2 appears to be a specific physiological thrombotic agent. Synthesis of TXA2 is elevated in patients with diabetes mellitus of types I and II and in hypertensive patients. TXA2 has a half-life of about 30 s under physiological conditions. Prostacyclin (PGI2) is formed in the vessel walls. Its action is antagonistic to TXA2, that is, it inhibits platelet aggregation and dilates the blood vessels. Synthesis of PGI2 is depressed in the presence of the classical 4 main risk factors for atherosclerosis: arterial hypertension, hyperlipoproteinaemia, smoking and diabetes mellitus. PGI2 has a half-life of about 3 min under physiological conditions. Since TXA2 and PGI2 are very labile and thus extremely difficult to measure, it is at present usual to measure their stable metabolites thromboxane B2 (TXB2) and 6-ketoprostaglandin F1.alpha. (6-keto-PGF1.alpha.). Radioimmunological measurement (RIA) of TXB2 in plasma requires no preliminary work, but radioimmunological measurement of 6-keto-PGF1.alpha. in plasma requires prior extraction and concentrating, since the concentration of 6-keto-PGF1.alpha. in the plasma is usually below the detection limit of commercial RIA kits. This paper describes standardized conditions for drawing the blood sample, a simple method of extraction from plasma and the reliability of two commercial RIA kits with 125I tracer in measuring TXB2 and 6-keto-PGF1.alpha. in plasma.