Impairment and Protection of Endothelium-Dependent Relaxation in Aortae of Various Strains of Spontaneously Hypertensive Rats

Summary: Endothelium-dependent relaxations of aortae from various strains of spontaneously hypertensive rats (SHR) were studied using SHR, stroke-prone SHR (SHRSP), and malignant SHRSP (M-SHRSP) of the Okamoto strain. Blood pressure of the rats was higher in the order of M-SHRSP > SHRSP > SHR. The endothelium-dependent relaxation of the aorta was impaired in these hypertensive rats compared with Wistar-Kyoto (WKY) rats. The impairment was age dependent and, when compared at the same age, greater in the following order: M-SHRSP > SHRSP > SHR. The impairment was prevented completely by antihypertensive treatment from the age before the blood pressure rises. It is concluded that the impairment of the endothelium-dependent relaxation is secondary to the maintained hypertension. Both the intensity and the duration of the hypertension are the determining factors of the degree of impairment.