cyclic-gmp and evocarpine

The effect of evocarpine (EVO), a quinolone alkaloid isolated from Evodiae fructus, on Ca2+-blocking activity has been examined. In the isolated rat thoracic aorta evocarpine significantly inhibited the contraction induced by 60 mM K+ with an IC50 of 9.8 microM, and that induced by external Ca2+ in the depolarized muscle in concentrations of 10-100 microM. The relaxant effect of evocarpine and verapamil was antagonized by Bay K8644. The increase of 45Ca2+-influx induced by 60 mM K+ was significantly inhibited by 100 microM evocarpine. In the isolated rabbit thoracic aorta 100 microM evocarpine had no effect on the norepinephrine-induced contraction in normal medium or on the phasic contraction in Ca2+-free medium or on the transient relaxation induced by activation of the Na+ pump. The content of cyclic AMP or cyclic GMP was unchanged. These results suggest that evocarpine inhibits Ca2+ influx through voltage-dependent calcium channels.

Topics: Alkaloids; Animals; Aorta, Thoracic; Biological Transport, Active; Calcium Radioisotopes; Carotid Arteries; Cyclic AMP; Cyclic GMP; Guinea Pigs; In Vitro Techniques; Isometric Contraction; Male; Muscle Relaxation; Muscle, Smooth, Vascular; Norepinephrine; Potassium; Quinolones; Rabbits; Rats; Rats, Inbred Strains; Sodium