Effects of intermittent vomitoxin exposure on body weight, immunoglobulin levels and haematuria in the B6C3F1 mouse

Continuous dietary exposure of female B6C3F1 mice to the trichothecene vomitoxin (VT) results in reduced body weight gain, elevated production of serum immunoglobulin A (IgA), kidney mesangial IgA deposition and glomerulonephritis. To assess whether intermittent consumption of dietary VT, as might occur during natural animal and human exposures, has similar effects to those for continuous consumption, a comparison was made between two schedules of dietary exposure. Female B6C3F1 mice were fed for 13 weeks with either a semipurified AIN-76A diet containing 20 ppm VT continuously or with 20 ppm VT intermittently (every other week). The effect these diets had on body weight gain, serum immunoglobulin (Ig) profile, mesangial Ig deposition and haematuria were assessed and compared with each other as well as with mice fed a control diet. Reduced body weight gains in the treatment groups were seen as early as 2 weeks. After week 4, the mean body weight of the intermittent group appeared higher than the continuous group during the weeks when it was fed a control diet, but dropped to continuous group levels during the weeks they were fed VT. Serum IgA levels in the intermittent group remained at control levels and were significantly lower than the continuous group during the course of the study. In contrast, serum IgG and serum immunoglobulin M (IgM) levels for the intermittent and continuous groups were significantly decreased compared with control. Mesangial IgA deposition was significantly lower in the intermittent group compared with the continuous group, and had levels comparable to mice on the control diet. Haematuria was significantly greater in both treatment groups compared with control at weeks 5 and 13 when the intermittent group was fed VT containing diet, but haematuria in the intermittent group dissipated at week 10 when it was fed control diet. The results presented here suggest that the type of dietary exposure regimen is critical in determining the extent of toxic effects induced by VT. Thus, when animal models are used for assessing the toxic effects of mycotoxins, it may be useful to consider the effects of intermittent and sporadic exposure.