Inhibitory action of prostaglandin E1 on smooth muscle contraction and calcium responses

The relation between the inhibitory action of prostaglandin (E1 (PGE1) and external Ca concentration was investigated using the guinea-pig isolated ureter and the perfused central artery of the rabbit isolated ear. PGE1 20 ng/ml reduced the ureteral contraction evoked by a single electrical stimulation. This inhibitory action of PGE1 was enhanced with a decreased external Ca concentration. PGE1 100 ng/ml also reduced Ca-induced contracture of the ureter depolarized in Ca-free K(80 mM)-Krebs' solution. Furthermore, PGE1 50 ng/ml inhibited the responses of peripheral vascular resistance to noradrenaline, and this effect increased with a reduced external Ca concentration.