The main pungent component of wasabi (Eutrema japonica) is known to be isothiocyanate and its derivatives, volatile substances. Allyl isothiocyanate (AITC) accounts for more than half of isothiocyanate derivatives. However, there is a little information on the effects of AITC on the immune system by analyzing the number of white blood cells (WBCs) over the course of days of AITC administration. In the present study, we studied the effects of AITC (dose=20 mg/kg body weight/day for 10 days, subcutaneous: s.c.) on the number of WBCs (total WBCs, lymphocytes, monocyte, neutrophil, basophil and eosinophil) and plasma corticosterone concentrations in adult male rats. Administration of AITC decreased significantly the number of total WBCs on days 1-4 post s.c. injection by 25-27%. Administration of AITC also decreased the number of lymphocytes on days 1-10 by 21-36% and monocyte on days 1-8 by 28-78%. However, administration of AITC increased the number of neutrophil on days 8-10 by 61-112%. AITC did not change the number of eosinophil and basophil. Plasma corticosterone concentrations during the experimental period were 4.7-8.4 times significantly higher in the AITC group than in the control group, indicating that AITC induced stress-responses. The relative weights of thymus and adrenals per body weight were significantly lower and clearly higher in the AITC group than in the control group, respectively. These results suggest that AITC-mediated stress-responses are at least in part attributable to changes in the number of circulating WBCs.
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