Importance of the adrenal cortex for development and maintenance of hypertension in spontaneously hypertensive rats

Adrenal regeneration following complete bilateral adrenalectomy in spontaneously hypertensive rats (SHR) was used to study the significance of glucocorticoid and mineralocorticoid hormones for the development and maintenance of hypertension. Pre-hypertensive (5 weeks of age) and hypertensive (10 and 16 weeks of age) male SHR underwent adrenalectomy (ADN) and were kept on 0.9% NaCl. The rats were ether stressed at various intervals to assess adrenal steroid production. Following ADN of all three age groups the development or maintenance of hypertension depended on the presence of adrenal regenerates. Animals without signs of adrenal regeneration remained or became normotensive. There was a significant correlation between plasma corticosterone levels following ether stress and blood pressure. Aldosterone and corticosterone production of regenerates and of adrenal cortex of intact SHR was studied in vitro. Under basal condition and following ACTH stimulation both tissues produced similar amounts of corticosterone, however considerably less aldosterone was secreted by regenerates. Betamethasone substitution in adrenalectomized rats caused a dramatic increase of blood pressure which was attenuated by L-propranolol. Aldosterone had no significant effect on blood pressure. It is concluded that glucocorticoids play a permissive role in the development of hypertension presumably via alteration of sympathetic neurotransmission.