Inhibition by methoxyverapamil of the responses of smooth muscle from spontaneously hypertensive and normotensive rats

Inhibition by methoxyverapamil (D 600) of the responses to norepinephrine (NE) and KCl of vascular (carotid and iliac arteries and aortae) strips and vasa deferentia from spontaneously hypertensive (SHR) and normotensive rats (WKY) were compared. The responses of aortic and carotid arterial strips from SHR to NE and KCl were inhibited to a lesser extent by low concentrations of D 600 (≤10–⁶M). The isolated preparations of the iliac arteries and the vasa deferentia showed no differences in their susceptibility to inhibition by D 600. The responses to NE and KCl in calcium-free solutions of vascular strips from WKY were generally resistant to inhibition by D 600 (10–⁶M) in ontrast to those from SHR which were markedly inhibited by D 600. Our results demonstrate that while the inhibitory action of D 600 on calcium movement may succeed in distinguishing vascular responses of SHR from those of WKY, the inhibitory pattern varies with different tissues and with experimental variations of calcium levels.