The subacute effects of dihydrocapsaincin (DHC) and capsaicin (CAP) (dose = 3 mg/kg body weight per day for 10 days, subcutaueous) on the number and distribution of white blood cells (WBCs) were studied in male adult rats. The administration of DHC and CAP for 10 days decreased significantly the number of total WBCs, lymphocytes and monocyte, and increased significantly the number of the neutrophil and eosinophil without changing the number of basophil. The administration of DHC significantly decreased thymus weight and increased adrenal weight, showing that DHC induced thymus atrophy and adrenal hypertrophy. These results suggest that capsaicinoids induced the decrease of acquired immunity responses and these phenomena may have in part participated in capsaicinoidsinduced stress-responses in rats.

-Red peppers are used as a spice for enhancing the palatability of foods. Two major capsaicinoids, dihydrocapsaicin (DHC) and capsaicin (CAP) are responsible for up to 90% of the total pungency of pepper fruits. These capsaicinoids are known to enhance energy metabolism and thermogenesis. However, there is a little information on the effects of capsaicinoids on the lipolysis and carbohydrate metabolism. We studied the effects of DHC and CAP on plasma glucose, free fatty acid (FFA) and glycerol concentrations in rats. Male six-week-old Sprague Dawley rats were divided into the DHC, CAP and control groups. Each capsaicinoid (dose = 3 mg/kg BW/day) was subcutaneously administered to rats for 10 days. DHC increased markedly plasma glucose, FFA and glycerol concentrations on day 1-10 by 14-35%, 61-103% and 108-174%, respectively, as compared with those of the control group. CAP increased relatively plasma glucose concentrations on day 1-3 by 15-17%, as compared with the control group.groups. On the contrary, CAP did not change plasma FFA and glycerol concentrations on day 1-3. However, CAP increased markedly plasma FFA and glycerol concentrations on day 7-10 by 54-89% and 92-98%, respectively, as compared with the control group. DHC and CAP did not change the weights of white (perirenal and periepididymal) and brown (interscapular) adipose tissues. In conclusion, the effects of capsaicinoids on plasma glucose, FFA and glycerol concentrations were relatively higher in the DHC than in the CAP, and capsaicinoids did not change the weight of white and brown adipose tissues.