In vivo and in vitro effects of mercuric chloride and sodium selenite on some non-specific immune responses of blue gourami, Trichogaster trichopterus (Pallus)

Abstract

The in vivo and in vitro effects of mercuric chloride and sodium selenite on the non-specific immunity of blue gourami, Trichogaster trichopterus were studied. Kidney lysozyme activity in fish treated with 0·09 ppm Hg2+ for two weeks was significantly higher than the control, whereas the plasma lysozyme activity remained unchanged. In contrast, all SeO3 2--treated fish showed no statistical difference in the kidney and plasma lysozyme activities after two weeks of exposure, except 0·5 ppm SeO3 2--treated fish, which had a higher lysozyme activity in plasma. The zymosan-stimulated chemiluminescent (CL) response of head-kidney cells isolated from the naive fish was inhibited in the presence of Hg2+. This was decreased to about 50% and 10% of the control at 0·045 ppm and 0·09 ppm Hg2+ respectively. On the other hand, the CL response of the head-kidney cells from the naive fish incubated with 4 ppm SeO3 2- was enhanced significantly. However, the CL response of the head-kidney cells isolated from the fish that were exposed to either Hg2+ or SeO3 2- for 2 weeks showed no statistical difference to control. The in vivo effect of Hg2+ and SeO3 2- on the natural bactericidal activity of plasma was tested by using a fish pathogen, Aeromonas hydrophila (strains L37 and PPD134/91). At 0·09 ppm Hg2+, the colony forming unit (cfu) counts of the A. hydrophila were significantly lower than the control. For the 0·1 ppm SeO3 2--treated fish, a higher cfu count was encountered for strain L37 but not for strain PPD134/91. On the contrary, 0·5 ppm SeO3 2- caused no change in the cfu count for strain L37 but decreased significantly the count in strain PD134/91. © 1996 Academic Press Limited.