Elevated tyrosine hydroxylase mRNA levels in the adrenal medulla of spontaneously hypertensive rats.

We investigated the expression of tyrosine hydroxylase (TH) mRNA and its activity in the adrenal medulla of spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). The TH mRNA levels were determined by Northern blot and dot blot analyses. The TH activity and the expression of TH mRNA in the adrenal medulla of SHR were significantly higher than those of WKY (P < 0.01). These results suggested that the hypertension of SHR may be related to the high activity of TH due to the high level of TH mRNA, which increases epinephrine and norepinephrine levels in the adrenal medulla.