Metabolism of Highly unsaturated Fatty Acids to Prostaglandins and their Physiological Activities in Fish.

众所周知，人类血小板将花生四烯酸(AA)转化为前列腺素(PGs)，特别是血栓素A_2(TXA_2)，这是一种强有力的血液聚集诱导剂。尽管血栓细胞被认为是鱼类血液中的凝血细胞，类似于哺乳动物的血小板，但鱼类血栓细胞中PGs的合成仍不清楚。因此，本研究旨在阐明鲤鱼、虹鳟鱼和红鱼的血小板中外源AA、二十碳五烯酸(EPA)和二十二碳六烯酸(DHA)合成PG的能力，并与人类血小板的合成能力进行比较。鲤鱼和虹鱼的血液来自背主动脉，红鱼的血液来自Cuvierian导管。制备富含血栓细胞血浆(TRP)，与N-羟乙基哌嗪-N‘-2-乙磺酸(HEPES)缓冲液混合，离心后再悬浮。洗涤后的颗粒与C标记的高度不饱和脂肪酸(AA、EPA和DHA)孵育。洗涤的人血小板主要将AA转化为血栓素B_2，而洗涤的鲤鱼和团鱼的血小板则将AA转化为PGF_2；PGE_2、PGE_2和PGD_2，洗涤虹鱼AA对这三种PGs，EPA对TXB_3。据此推测，人的血小板与鱼的血栓细胞，甚至鱼种之间PG的合成存在差异。最后，认为人的血小板与鱼的血栓细胞在PG的合成上的差异导致了不同的血液聚集行为。

It is well known that human platelets convert arachidonic acid (AA) to prostaglandins (PGs), especially to thromboxane A_2 (TXA_2), which is a potent inducer of blood aggregation. Although thrombocytes are considered to be the clotting cells of fish blood similar to mammalian platelets, the syntheses of PGs in fish thrombocytes still remain unclear. Therefore, the present study was designed to clarify the capacity of PG syntheses from exogenous AA, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) in carp, rainbow trout, and red sea bream thrombocytes, and compared with that in human platelets.The blood of carp and rainbow trout was collected from dorsal aorta, and that of red sea bream from cuvierian duct. The thrombocyte-rich plasma (TRP) was prepared, mixed with N-hydroxyethylpiperazine-N'-2-ethanesufonic acid (HEPES) buffer, centrifuged, and resuspended. The washed pellets were incubated with ^<14>C-labelled highly unsaturated fatty acids (AA, EPA, and DHA).Washed human platelets mainly converted AA to thromboxane B_2, however, washed carp and red sea bream thrombocytes converted AA to PGF_<2<alpha>>,PGE_2, and PGD_2, and washed rainbow trout AA to these three PGs and EPA to TXB_3. Accordingly, it is assumed that there are differences in PG syntheses between human platelets and fish thrombocytes and even among the fish species, Finally, it is considered that the differences in PG syntheses among human platelets and fish thrombocytes cause the different behaviors in the blood aggregation.