Involvement of tyrosine hydroxylase up regulation in dexamethasone-inducedhypertension of rats

We investigated the effect of dexamethasone (DEX) on tyrosine hydroxylase ( TH) mRNA level, and TH activity and catecholamine levels in the adrenal med ulla of the rat. DEX (1 mg/kg/day, s.c.) was administered for 2 days, and a control group was given corn oil. DEX significantly increased systolic blo od pressure. TH mRNA level, TH activity, epinephrine level, and norepinephr ine level in the adrenal medulla of DEX-treated rats were significantly hig her than those of control rats. Also, epinephrine and norepinephrine levels in plasma were significantly higher in DEX-treated rats than in controls. alpha-Methyl-p-tyrosine prevented the DEX-induced blood pressure increase. These results suggest that the catecholamine synthetic pathway may be invol ved in DEX-induced hypertension. (C) 2000 Elsevier Science Inc. All rights reserved.