Exposure to stress : Differential vascular adaptive response in spontaneously hypertensive and Wistar rats: Role of nitric oxide, and prehypertensive and hypertensive states

Stress-induced vascular adaptive response in SHR was investigated, focusing on the endothelium. Noradrenaline responses were studied in intact and denuded aortas from 6-week-old (prehypertensive) and 14-week-old (hypertensive) SHR and age-matched Wistar rats submitted or not to acute stress (20-min swimming and 1-h immobilization 25 min apart), preceded or not by chronic stress (2 sessions 2 days apart of 1-h day immobilization for 5-consecutive days). Stress did not alter the reactivity of denuded aorta. Moreover, no alteration in the EC50 values was observed after stress exposure. In intact aortas, acute stress-induced hyporeactivity to noradrenaline similar between strains at both age. Chronic stress potentiated this adaptive response in 6- and 14-week-old Wistar but not in 6-week-old SHR, and did not alter the reactivity of 14-week-old SHR. Maximum response (g) in intact aortas [6-week-old: Wistar 3.25 ± 0.12, Wistar/acute 1.95 ± 0.12*, Wistar/chronic 1.36 ± 0.21*+, SHR 1.75 ± 0.11, SHR/acute 0.88 ± 0.08*, SHR/chronic 0.85 ± 0.05*; 14-week-old: Wistar 3.83 ± 0.13, Wistar/acute 2.72 ± 0.13*, Wistar/chronic 1.91 ± 0.19*+, SHR 4.03 ± 0.17, SHR/acute 2.26 ± 0.12*, SHR/chronic 4.10 ± 0.23; inside the same strain: *P < 0.05 relate to non-stressed rat, +P < 0.05 related to acute stressed rat; n = 6–18]. Independent of age and strain, l-NAME and endothelium removal abolished the stress-induced aorta hyporeactivity. Conclusion: The vascular adaptive response to stress is impaired in SHR, independently of the hypertensive state. Moreover, this vascular adaptive response is characterized by endothelial nitric oxide-system hyperactivity in both strains.