IN-VITRO STUDIES ON THE REGULATION OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) MACROPHAGE RESPIRATORY BURST ACTIVITY

Modulation of the respiratory burst activity of head kidney macrophage s isolated from rainbow trout (Oncorhynchus mykiss) was observed follo wing treatment with several biologically active substances. Macrophage -activating factor (MAF) induced the highest increment in respiratory burst activity relative to treatment with lipopolysaccharide (LPS), tu mor necrosis factor alpha (TNF alpha) or beta-glucans from Saccharomyc es cerevisiae. Increased responses were more evident when these molecu les were combined in pairs. Negative regulation of respiratory burst a ctivity was observed when diMePGE(2) was added to the macrophages, wit h maximal inhibition seen using a concentration of 2.6 mu M. Inhibitio n was also seen using stimulated macrophages, either by co-incubation of stimuli and diMePGE(2) or by adding diMePGE(2) to previously stimul ated cells. The inhibitory effect on macrophages was detectable within 3 h of incubation with diMePGE(2) and by 24 h the level of the respon se was even lower than that from unstimulated (control) macrophages. O f significance was the finding that the inhibitory effect of prostagla ndin on macrophage function could be overcome by co-incubation with st imulatory molecules or by pre-treatment with MAF and LPS or MAF and TN F alpha. Thus, the regulation of macrophage activation in fish is like ly to be as complex as in mammals. Copyright (C) 1996 Elsevier Science Ltd.