12(S)-Hydroxy-5,8,10 (Z,E,E)-heptadecatrienoic acid (HHT) is preferentially metabolized to its 12-keto derivative by human erythrocytes in vitro.

The metabolism of [1-14C]-labelled 12 (S)-hydroxy-5,8,10 (Z,E,E)-heptadecatrienoic acid (HHT) by crude 15-hydroxyprostaglandin dehydrogenase (PGDH) fractions from swine kidney and human erythrocytes has been investigated. HPLC radiochromatography analysis revealed that HHT was extensively converted into three metabolites by swine kidney cytosol in the presence of NAD+. They were identified by combined GLC mass spectrometry as 12-keto-5,8,10 (Z,E,E)-heptadecatrienoic acid (KHT), 12-keto-5,8 (Z,E)-heptadecadienoic acid and 12 (RS)-hydroxy-5,8 (Z,E)-heptadecadienoic acid, respectively. In contrast, HHT was metabolized only to the 12-keto derivative by human erythrocyte cytosol supplemented with NADP+, and HHT turnover was found to be enhanced severalfold when compared to prostaglandins E2 (PGE2) or F2 alpha. Since PGE2 was also converted only into 15-keto-PGE2, and no metabolism of KHT was detected with NADPH, there is probably no 15-ketoprostaglandin delta 13-reductase activity in human erythrocytes. Biosynthetic KHT (0.5-5 microM) inhibited the aggregation of human platelets to almost all agonists, probably by raising intracellular cAMP. KHT (between 0.01 and 1 microM) also induced the chemotaxis of human polymorphonuclear leukocytes. Among other still unrecognized effects, these biological activities of KHT may be of physiological significance with respect to its presumably exclusive formation in the blood. The potential use of KHT for monitoring thromboxane synthase activity in vivo is discussed.