15-hydroxy-11-alpha-9-alpha-(epoxymethano)prosta-5-13-dienoic-acid and efonidipine

Spasmolytic effects of efonidipine hydrochloride (efonidipine) on high K(+)-, U46619- and 3,4-diaminopyridine (3,4-DAP)-induced contractions were evaluated in isolated canine coronary, artery, and were compared with the effects of nifedipine and nisoldipine. Efonidipine (0.3-30 nM), nifedipine (1-300 nM) and nisoldipine (0.1-100 nM) each relaxed the contractions induced by high K+ and U46619. However, relaxation produced by efonidipine was slower than that produced by nifedipine or nisoldipine. The rank order of potency of these drugs for U46619-induced contraction was efonidipine > or = nisoldipine > nifedipine, whereas in high K(+)-induced contraction, it was nisoldipine > efonidipine > nifedipine. Thus, the relaxing effect of efonidipine on U46619-induced contraction appeared to be more potent than its effect on high K(+)-induced contractions, when compared with the effects of nifedipine and nisoldipine. These three drugs also suppressed 3,4-DAP-induced rhythmic contractions. However, a marked time-dependent increase in potency was only observed for efonidipine, and was similar to its time-dependent effect on high K(+)- and U46619-induced contractions. Efonidipine did not change the contraction cycle length whilst suppressing the peak contractions. On the other hand, lower concentration of nifedipine at 3 nM and nisoldipine at 1 nM significantly shortened the cycle length. These results suggest that efonidipine may be an effective agent for the treatment of angina pectoris. The high potency of efonidipine for U46619-induced contractions will provide some advantages in the clinical use of this compound on thromboxane A2-mediated coronary vasoconstriction.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 4-Aminopyridine; Amifampridine; Animals; Arteries; Calcium Channel Blockers; Coronary Vessels; Dihydropyridines; Dogs; In Vitro Techniques; Nitrophenols; Organophosphorus Compounds; Potassium; Prostaglandin Endoperoxides, Synthetic; Thromboxane A2; Vasoconstrictor Agents

We studied the effects of efonidipine hydrochloride (efonidipine), a 1,4-dihydropyridine derivative, on contractions induced by high-K+ solution (high K+), serotonin (5-HT), U46619, which is a stable analog of thromboxane A2, and endothelin-1 (ET-1) in comparison with those of nifedipine and nisoldipine in porcine coronary arteries. The effects of the drugs were compared after 1- and 3-h incubations. Efonidipine, nifedipine, and nisoldipine each inhibited the contractions induced by these vasoconstrictors. The inhibition of high-K(+)- and 5-HT-induced contractions by efonidipine, but not by nifedipine and nisoldipine, increased when the incubation time was prolonged, whereas the inhibition of U46619- and ET-1-induced contractions was not altered. The potency of efonidipine on U46619- and ET-1-induced contractions was greater than that of nifedipine and equivalent to that of nisoldipine. Thus the inhibitory effect of efonidipine on U46619- and ET-1-induced contractions seems to be stronger than its effects on high-K(+)- or 5-HT-induced contractions, in contrast to the effects of other dihydropyridines. In an additional series of experiments, efonidipine did not inhibit U46619-induced contractions in Ca2(+)-free solution or in the presence of nifedipine. Moreover, efonidipine did not inhibit the specific binding of [3H]SQ 29,548, a thromboxane A2 antagonist, to porcine coronary arterial membrane. Therefore we think that the inhibitory effect of efonidipine on contractions induced by vasoconstrictors was caused by blockade of Ca2+ influx through L-type Ca2+ channels. However, some unknown mechanism(s) in addition to this effect on Ca2+ channels may contribute to the effect of efonidipine on U46619- and ET-1-induced contractions.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Binding, Competitive; Calcium Channel Blockers; Coronary Vessels; Dihydropyridines; Endothelin-1; In Vitro Techniques; Muscle Contraction; Muscle, Smooth, Vascular; Nifedipine; Nisoldipine; Nitrophenols; Organophosphorus Compounds; Potassium; Prostaglandin Endoperoxides, Synthetic; Serotonin; Swine; Thromboxane A2; Vasoconstrictor Agents