Prostaglandin Endoperoxides. A New Concept Concerning the Mode of Action and Release of Prostaglandins

Abstract

Methods were developed for quantitative determination of the three major metabolites of arachidonic acid in human platelets, i.e., 12L-hydroxy-5,8,10,-14-eicosatetraenoic acid (HETE), 12L-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and 8-(1-hydroxy-3-oxopropyl)-9,12L-dihydroxy-5,10-heptadecadienoic acid (PHD). Aggregation of washed platelets by thrombin was accompanied by release of 1163-2175 ng/ml of HETE, 1129-2430 ng/ml of HHT, and 998-2299 ng/ml of PHD. The amount of PGG2 (prostaglandin G2) produced as calculated from the sum of the amounts of its metabolites (HHT and PHD) was 2477-5480 ng/ml. In contrast, the amounts of PGE2 (prostaglandin E2) and PGF2. (prostaglandin F2.) released were approximately two orders of magnitude lower. In this system, the prostaglandins thus exert their biological action through the endoperoxides, which are almost exclusively metabolized to nonprostanoate structures and only to a small extent to the classical prostaglandins.Platelets from subjects given aspirin produced less than 5% of the above mentioned amounts of HHT and PHD, whereas the production of HETE was stimulated about 3-fold. This provides additional evidence for our earlier proposal tHamberg, M., Svensson, J., Wakabayashi, T. & Samuelsson, B. (1974) Proc. Nat. Acad. Sci. USA 71, 345-3491 that the anti-aggregating effect of aspirin is through inhibition of PGG2 formation.In a recent paper (1) we showed that the prostaglandin endoperoxides, PGG2 and PGH2, in low concentrations induce aggregation of human platelets and that they are released during thrombin-induced aggregation. Together with the known effects of inhibitors of prostaglandin biosynthesis on platelets, this indicated a physiological role of endoperoxides in platelet function and gave information on the mechanism of action of, e.g., aspirin (1, 2). With a similar technique, it was also demonstrated that aggregation induced by collagen, epinephrine, and arachidonic acid was accompanied by release of the intact endoperoxides (3).We recently studied the transformation of [ [5,6,8,9,11,12,14,Arachidonic acid was prepared as previously described (5). [3,3,4,4-2H4]PGE2 and [3,3,4,4-2H4]-PGF2a were generously provided by Dr. U. Axen, The Upjohn Co., Kalamazoo, Mich. Thrombin (TopostasinO) was purchased from Hoffmann-La Roche Co.Quantitative Determination of 12L-Hydroxy-6,8,10,14-Eicosatetraenoic Acid (HETE). 5,6,8,9,11,12,14,

Further studies on the effects of flavine adenine dinucleotide on the platelet functions.

“…The results of this study showed that the synthesis of thromboxane was not inhibited by FAD at any time of incubation periods, while it was markedly inhibited by aspirin, which is a well known inhibitor of cyclooxygenase (Hamberg, Svensson and Samuelsson 1974). A part of the results obtained in the present experiments is shown in Fig.…”

Biosynthesis of Thromboxane B2 and 12‐l‐Hydroxy‐5,8,10‐heptadecatrienoic Acid in Human Platelets

“…Thromboxane B2 is apparently formed from its unstable precursor thromboxane A2 [3]. The generation of thromboxane AZ required the presence of an active platelet microsomal fraction.…”

“…Its formation was suggested to play a key role in arachidonic-acid-induced platelet aggregation [3]. In contrast, no distinct physiological role has yet been observed or suggested for 120H-17:3.…”

“…Prostaglandin E2, 1 la,lS(S)-dihydroxy-9-ketoprosta-S-cis,l3-trans-dienoic acid; prostaglandin Fz., 9a,l Ia,lS(S)-trihydroxyprosta-S-cis,l3-trans-dienoic acid; prostaglandin D2,9a, 15(S)-dihydroxy-l1 -ketoprosta-5-cis,l3-trans-dienoic acid ; prostaglandin AI, 1S(~-hydroxy-9-ketoprosta-S-cis,Z0,13-trans-trienoic acid ; prostaglandin H2, 9a,l 1 a-epidioxy-lS(S)-hydroxy-S-cis,l3-trans-prostadienoic acid; prostaglandin Gz, 9a,l la-epidioxy-IS(S)-hydroperoxy-5-cis, 13-trans-prostadienoic acid; 120H-17 : 3, 12.~-hydroxy-5,8,10-heptadecatrienoic acid: 12OH-20 :4, 22-~-hydroxy-5,8,10,14-icosatetraenoic acid; thromboxane Bz, hemiacetal derivative of 8-(l-hydroxy-3-oxopropyl)-9,12-~-dihydroxy-5,lO-heptadecadienoic acid; thromboxane AZ presumed structure [3] is: 5 H first product was formed from arachidonic acid by a novel lipoxygenase reaction, while the latter two products were obtained by the action of fatty acid cyclooxygenase. The latter two products were also obtained in incubations of the prostaglandin endoperoxide intermediates H2 or G2 with platelet microsomes [3,4].…”

“…Thromboxane Az is a powerful vasoconstrictor of the isolated rabbit aorta and induces platelet aggregation [3,4]. Its formation was suggested to play a key role in arachidonic-acid-induced platelet aggregation [3].…”