The purpose of this study was to elucidate the effects of dexamethasone, a synthetic glucocorticoid, on the immune system by analyzing the number of white blood cells (WBCs) over the course of hours and days of dexamethasone administration. Dexamethasone was given as either a single dosage [1.0 mg/kg body weight (BW); subcutaneous injection (s.c.)] or as a daily dosage (1.0 mg/kg BW per day; s.c.) for 10 days for the hourly and daily assessment of changes in the number of white blood cells, respectively. A single administration of dexamethasone markedly decreased the number of total WBCs, as well as the number of lymphocyte, monocyte, neutrophil and eosinophil subsets with a nadir at 8 hr post-injection. The number of these cells recovered to the control levels at 24 hr. The numbers of total WBCs, lymphocytes, monocyte, eosinophil and basophil were reduced by the daily administration of dexamethasone. However, the number of neutrophil was significantly higher at days 2 and 8 after the injection. These results suggest that glucocorticoid-mediated immunosuppressions are at least partly attributable to quantitative changes in the number of circulating WBCs.

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.

-The aim of this study was to elucidate whether dietary zinc-deficiency and its recovery play a role in controlling autonomic thermoregulation. We investigated the effects of dietary zinc-deficiency and its recovery on autonomic thermoregulation by measuring the rectal temperature, an index of deep body temperature. The weaned male Sprague Dawley rats were randomly divided into the dietary zinc-deficient diet (0.6 mg zinc/kg diet) group and the control diet (35.2 mg zinc/kg diet) group, and were fed for 4 weeks. In the recovery period, the rats of two groups were fed with the control diet for 3 weeks. The rectal temperature was significantly decreased throughout the period of zinc-deficiency and the hypothermic responses during the experimental period were recovered to the control group levels at least within 1 week in the recovery process from dietary zinc-deficiency. These results suggest that the deep temperature in rats was clearly associated with the dietary zinc intake levels.