Ca2+ influx in spontaneously hypertensive rats is sensitive to calcium antagonists

Upon perfusion with a solution containing Ca2+, after Ca2+-free perfusion, aortic rings from spontaneously hypertensive rats (SHR) responded with a contraction. The contraction was usually transient. When verapamil or nifedipine were added prior to and during Ca2+ repletion, the force developed was reduced to 25% of that of uninhibited contraction. Aortas from normotensive rats did not show comparable properties. These findings demonstrate that calcium influx in aortic smooth muscle of SHR occurs mainly via voltage-dependent calcium channels.