title: Effects of vinpocetine on cyclic nucleotide metabolism in vascular smooth muscle.
abstract: A novel vasodilating agent, vinpocetine (14-ethoxycarbonyl-(3 alpha,16 alpha-ethyl)-14,15-eburnamenine) inhibits Ca2+-dependent phosphodiesterase, selectively, among the three forms of cyclic nucleotide phosphodiesterase identified in the rabbit aorta. The concentration of vinpocetine producing 50% inhibition of Ca2+-dependent phosphodiesterase activity was approximately 21 microM, both in the presence and absence of Ca2+-calmodulin (CaM). Increasing the concentration of CaM in the presence of Ca2+ did not prevent vinpocetine-induced inhibition of Ca2+-dependent phosphodiesterase, thereby indicating that vinpocetine inhibited the enzyme by interacting with the enzyme and not with CaM. To determine the influence of vinpocetine-induced inhibition of Ca2+-dependent phosphodiesterase on cyclic nucleotide metabolism in vascular smooth muscle, cyclic nucleotide levels in isolated rabbit aortic strips were also investigated. Addition of vinpocetine produced dose-dependent increases in only the cyclic GMP levels and there was no significant effects on the cyclic AMP levels. These results provide pharmacological evidence that Ca2+-dependent phosphodiesterase mainly hydrolyzes cyclic GMP in vascular smooth muscle. Vinpocetine may induce vascular relaxation by increasing cyclic GMP contents in vascular smooth muscle through selective inhibition of Ca2+-dependent phosphodiesterase.
mesh_terms: D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases / Q000037:antagonists & inhibitors; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000037:antagonists & inhibitors; D000242:Cyclic AMP / Q000032:analysis; D006152:Cyclic GMP / Q000032:analysis; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009712:Nucleotides, Cyclic / Q000378:metabolism*; D011817:Rabbits; D014665:Vasodilator Agents / Q000494:pharmacology*; D014748:Vinca Alkaloids / Q000494:pharmacology*
chemical_list: D002147:Calmodulin; D009712:Nucleotides, Cyclic; D014665:Vasodilator Agents; D014748:Vinca Alkaloids; C013983:vinpocetine; D000242:Cyclic AMP; D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases; D006152:Cyclic GMP; D002118:Calcium