Comparative Study of Prostaglandin Synthesis and Blood Coagulation in the Fish

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Prostaglandin (PG) syntheses from the labelled highly unsaturated fatty acids were investigeted in washed thrombocytes suspensions of four species of marine fish, flounder, black sea bream, black rockfish, and red sea bream. When [1-^<14>C] -arachidonic acid (AA) was investigated with washed thrombocytes suspension, AA was mainly converted to PGF_<2alpha>, PGE_2, PGD_2 in all species. It was suggested that [1-^<14>C] eicosapentaenoic acid was mainly converted into PGs only in black rockfish thrombocytes, and the metabolites were mainly PGE_3 and PGD_3. However, [1-^<14>C] docosahexaenoic acid was not cyclized into PGs in all species. Aggragation behaviors of human platelets and carp, rainbow trout, and red sea bream thrombocytes were studied by an microscopic observation. Human platelets and all fish thrombocytes aggregated in the presence of ionophore A_<23187>, thrombin, and collagen, but did not aggregate in the presence of EPA, DHA, PGF_2, PGD_2 or ADP. Moreover, fish thrombocytes did not aggregate in the presence of TXA_2, PGG_2 , and PGH_2 whose induces the aggragation of human platelets. It was recognized that the inducers of thrombocytes aggregation appeared in the supernatant of carp thrombocytes suspension which aggregated by collagen. However, the structure of the inducers could not be determined.The endogeneous products extracted from the gill of red sea bream were isolated by high-performance liquid chromatography and identified as 12-hydroxyeicosatetraenoic acid, 12-hydroxyeicosapentaenoic acid, and 14-hydroxydocosahexaenoic by ultraviolet absorption spectra and gas chromatography-mass spectrometry. The endogeneous products of carp gill were also identified as 13-hydroxyoctadecadienoic acid, 12-hydroxyeicosatetraenoic acid, and 12-hydroxyeicosapentaenoic acid.