Bioassay of Prostacyclin and Thromboxane A2
Bioassay of the products of cyclo-oxygenation of arachidonic acid (AA) is not only a laboratory technique, it is also a way of biological thinking. Unlike phychicochemical techniques bioassay offers a continuous monitoring of changes in concentration of prostaglandins (PGs), prostacyclin (PGI2) and thromboxane A2 (TXA2) in blood of anesthetized animals or in the perfusate from isolated organs. The price which is paid for the devotion to bioassay is uncertainty about the real chemical nature of a substance which is assayed. The approximation is sometimes very near to the certainty but it never reaches this point. Therefore, we frequently refer to PGI2-like or TXA2-like substances instead of the firm statement — this is PGI2 and that is TXA2. However, this handicap may appear as an advantage of bioassay. A rabbit aorta contracting substance (RCS) had been described as an unstable metabolite of AA before cyclic endoperoxides (PGG2 and PGH2) and TXA2 were discovered. The existence of PGI2 was discovered only because of its “peculiar” behaviour in the bioassay system. Bioassay, when mastered, stimulates research because of its yet unexploited possibilities. Bioassay was created by pharmacologists and thus a number of pharmacological “tricks” are available to increase its specifity and sensitivity.
KeywordsPlatelet Rich Plasma Thromboxane Synthetase Collagen Strip Thromboxane Synthetase Inhibitor Platelet Clump
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