The aim of this study was to determine if pressor hyper-responsiveness is associated with the
hypertension that results from the ingestion of the
synthetic estrogen,
mestranol. Rats were fed a diet containing
mestranol for 6 months, while control rats were fed the same diet without
mestranol.
Catheters were then placed in the carotid artery and jugular vein of all rats, under
halothane anesthesia. When the rats had recovered from the
anesthesia, blood pressure was measured through the carotid
catheter in conscious rats. Each rat received IV
injections of
norepinephrine (NE) at 2, 4, 8, and 16 ng per 100 gm
body weight, and the pressor responses were recorded. The rats fed
mestranol had significantly higher arterial pressures than did the control rats. However, the pressor responses to NE were significantly less in the
mestranol-treated rats than in the controls, indicating that pressor hyper-responsiveness does not contribute to this form of
hypertension.