Sammendrag
The temperature, osmolality and heavy metal content of blood and tissues might be affected by the environment and the feed. In this study the potential effects of these factors on the cellular innate process, phagocytosis, of head kidney leukocytes were studied. Atlantic cod (800-1000g) were anesthetised, sacrificed, pieces of head kidney removed and the macrophage enriched leukocyte fraction isolated according to established procedures. Cells were further incubated in microwells in triplicates in the presence of homeotypic serum opzonised latex beads under different temperatures, osmolalities and heavy metal concentrations. The phagocytic capacity (number of phagocytic cells) and the phagocytic index (number of beads per cells) were found by counting the cells and beads in a microscope. The experimental incubations were done with a minimum of 6 animals. Phagocytic capacity and index increased at higher temperature. Hypoosmotic medium inhibited phagocytosis, there were a trend to inhibit also in hyperosmotic medium, albeit not significant in the range of osmolalities tested. Incubations with the heavy metals cadmium (CdCl2), zinc (ZnCl2) and copper (CuCl2) gave a significant reduction in phagocytic capacity and phagocytic index at higher concentrations. Lower concentrations of zinc and copper stimulated phagocytosis, whilst cadmium did not have any significant stimulatory effect at the concentrations used. The results suggest that phagocytosis of HK leukocytes can be modulated by factors such as temperature, osmolaility and heavy metals. In most conditions phagocytosis was inhibited, but at lower levels of heavy metals there were also a stimulatory effect
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