THE EFFECT OF EICOSANOIDS ON RAINBOW-TROUT, ONCORHYNCHUS-MYKISS, LEUKOCYTE PROLIFERATION

Proliferation of rainbow trout head kidney leucocytes in response to the mitogen phytohaemagglutinin-P (PHA-P) was modulated in the presence of inhibitors of eicosanoid synthesis and by exogenous eicosanoids. The presence of indomethacin, a cyclooxygenase inhibitor, resulted in a stimulatory effect, whereas the presence of nordihydroguiaretic acid, a lipoxygenase inhibitor, resulted in an inhibitory effect on mitogenicity. The addition of prostaglandins and lipoxins was also found to be inhibitory, whilst the addition of leukotrienes was stimulatory. Some class/series effects of the eicosanoids were also apparent. Prostaglandin E(2) was a more potent inhibitor than prostaglandin E(3), and proliferation was more sensitive to the effects of leukotriene B-4 than to leukotriene B-5. Whilst PHA-P was able to directly induce the release of prostaglandins from head kidney leucocytes, it did not induce the release of lipoxygenase products.