Study of the strontium response in isolated rat aorta

We have studied the effects of the cumulative application of Sr2+ in isolated rat aorta in a normal and in a Ca2+-free solution containing EDTA 1 mM. Sr2+ induced a concentration-dependent contraction which was reduced by verapamil (5 X 10(-6) and 10(-7) M) and lanthanum (1 and 2 mM). Sr2+ also induced a contraction in K+-depolarized medium. In aorta strips depleted of Ca2+ by several applications of noradrenaline (10(-6) M), Sr2+ induced a dose-response contraction in a Ca2+-free solution. These findings suggest that the influx of external Ca2+ is only partly responsible for the Sr2+-induced contraction and that another intracellular mechanism is involved in the response.