EFFECT OF LINDANE EXPOSURE ON RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) IMMUNITY .4. PREVENTION OF NONSPECIFIC AND SPECIFIC IMMUNOSUPPRESSION BY DIETARY VITAMIN-C (ASCORBATE-2-POLYPHOSPHATE)

The effect of the organochlorine insecticide lindane (gamma-hexachloro cyclohexane) administered intraperitoneally at 10 or 50 mg/kg body wt on some major immune functions of rainbow trout (Oncorhynchus mykiss) was examined. Fish were fed vitamin C as ascorbate-2-polyphosphate at a basal level (60 mg ascorbic acid(AA)-equivalent/kg of feed) or a hig h level (2000 mg AA-equivalent/kg) 1 month before lindane exposure and during the whole experiment, The aim of the experiment was to determi ne whether dietary vitamin C is able to prevent immunosuppression due to lindane. The concentration of ascorbic acid in organs and the circu lation was controlled, and the number of lindane residues in whole bod y was measured by gas chromatography. Nonspecific immune response was investigated through the determination of sera lysozyme and ceruloplas min; both were significantly modified by lindane exposure while the im mediate stimulating effects of vitamin C were observed. Cellular immun ity was investigated by determining the number of B lymphocytes (analy zed by cytofluorometry) and their ability to proliferate with mitogens . One month after exposure to lindane (10 mg/kg) the proportion of Ig( +) lymphocytes in head kidney was significantly decreased by the insec ticide. Higher levels of vitamin C (2000 mg/kg) led to a significant i ncrease in this parameter, Thus, vitamin C had a compensating effect o n the number of Ig(+) lymphocytes in exposed fish. Lindane at 10 mg/kg decreased the proliferation of B lymphocytes, but this was not confir med at 50 mg/kg. Vitamin C stimulated the proliferation for the latter concentration after 2 months of intake. In lindane-exposed fish, the PMA-induced chemiluminescent response of head kidney phagocytic cells was variable from one assay to another, while most of the time vitamin C acted as a stimulant. The humoral response to Yersinia ruckeri was not modified by lindane but was significantly increased by vitamin C f or 1 month after the antigen injection and thus 2 months after vitamin intake. (C) 1995 Academic Press, Inc.