Stress-induced secretion of ACTH and corticosterone during development of spontaneous hypertension in rats.

Plasma ACTH and corticosterone response to ether inhalation was examined in spontaneously hypertensive rats (SHR) and in normotensive Wistar-Kyoto (WKY) and Wistar control rats at 4, 8, 12 and 16 weeks of age. In SHR, blood pressure rose to hypertensive levels (above 150 mm Hg) between 5 and 8 weeks, whereas, in control animals, it did not exceed 140 mm Hg. Maximum plasma ACTH concentrations were measured 5 min after exposure to ether and plasma corticosterone values attained their maximum at 20 min. Stress-induced ACTH release was significantly elevated in SHR at 4 and 8 weeks. At 16 weeks of age, no difference in the ACTH response between the three strains could be detected. Correspondingly, 4-week-old SHR showed a more pronounced corticosterone release than Wistar and WKY, whereas 16-week-old SHR and control rats responded similarly. Hypothalamo-pituitary-adrenocortical response to ether stress is thus markedly enhanced in SHR during early development of hypertension.