Rainbow trout (<I>Oncorhynchus mykiss</I>) gill was found to generate three main lipoxygenase products, namely 12-hydroxyeicosatetraenoic acid (12-HETE), 12- hydroxyeicosapentaenoic acid (12-HEPE) and 14-hydroxydocosahexaenoic acid (14-HDHE) and to a lesser extent a single identifiable dihydroxy product, 8, 15-dihydroxyeicosatetraenoic acid (8,15-diHETE). All four compounds were structurally elucidated by gas chromatography-mass spectrometry. Variation in the eicosanoid profile was observed with respect to 12-HETE and 8,15-diHETE generation in density gradient centrifugation fractionated gill cells. In fish, eosinophilic granule cells (EGCs) have been considered to be equivalent to mast cells known to occur in all other vertebrate classes. These cell types share a number of common features including connective tissue distribution and degranualting behaviour, although equally, there are important differences. From the present study, the numbers of EGCs found in rainbow trout gill explant cultures following incubation with lipopolysaccharide (LPS) and tumour necrosis factor-α (TNF-α) increased significantly, suggesting that cytokines may mediate the differentiation and development of EGCs. Similarly, induction of fish stress by modification of environmental parameters appeared to cause an increase EGC accumulations in the gill. The discovery of the inducible cyclooxygenase enzyme (COX-2) in mammals came from initial studies examining the stimulated prostanoid generation in the presence of mitogens and hormones. Subsequently, specific drugs and antibodies have been developed allowing the clarification of inducible COX activity in a wide variety of cells and tissues. Fish macrophages, similarly generate increased amounts of prostaglandin E when stimulated with macrophage-derived factors and/or bacterial LPS, a response found to be inhibited by the COX-2 specific inhibitor, NS398, and by dexamethasone and cyclohexamide. These results imply the existence of an inducible COX activity in fish potentially homologous to mammalian COX-2.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:637290 |
| Date | January 1998 |
| Creators | Holland, J. W. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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