Noradrenaline and calcium induced tension in aortic strips of normotensive and spontaneously hypertensive rats.

Development of tension in aortic helical strips was studied using the male Kyoto Wistar normotensive (KNR) and age-, sex-matched spontaneously hypertensive rats (SHR) (8 to 10 weeks) to clarify the contractile response of vascular smooth muscle in SHR. In Ca2+-containing solution, noradrenaline-induced tension was smaller in SHR than in KNR. After washing the strips with Ca2+-free EGTA solution, the tension that developed by the addition of Ca2+ was greater in SHR than in KNR. Tension induced by the combination of Ca2+ and noradrenaline was the same between the KNR and SHR. It is assumed that these differences between the KNR and SHR aortic strips may be attributed to the abnormal contractility of the vascular smooth muscle in SHR.