Characteristic of the Vincanine Relaxing Action on the Contractive Activity of Aortic Smooth Muscle Cells

Background & Aim: The special attention is paid to natural biologically active compounds of plant origin, which have a wide range of pharmacological effects and specifically interact with various types of ion channels. The relaxant effect of some diterpenoid alkaloids on the Ca channels of smooth muscle cells has been studied. The aim of this work was to study the mechanism of the relaxant effect of vincanine. Methods: Isolated preparations of smooth muscle segments of the aorta of white outbred rats (200 g-250 g) were used. The prepared aortic segment was placed into a special experimental chamber with a volume of 5 ml, where it was fixed with a silver wire between the rod of an electromechanical transducer (FT.03, Grass, USA). The contractile activity of the aorta preparations was recorded using a PIIT amplifier (Grass, USA) and an Endim 621.02 recorder (Germany). We used phenylephrine verapamil and ethylene glycol bis-aminoethyl tetra acetate from Sigma (St. Louis, Mo, USA). Results: The indole alkaloid vincanine in a wide concentration range did not affect the basal tone of the rat aorta preparations. The studied alkaloid effectively relaxed the preparations of the aorta previously contracted with hyperpotassium solutions. The relaxing effect of vincanine was dose-dependent, and with an increase in the alkaloid concentration in the range of 10 mu M-50 mu M, the force of contraction of the rat aorta preparation induced by 50 mM KCl decreased from 15.7%-4.2% to 93.6%-3.6%. The EC50 value at which vincanine relaxed the aortic preparation by 50% was 16.3 mu M. Conclusion: The blockade of the receptor-driven Ca-2+ channels may also be involved in providing the relaxant effect of the investigated alkaloid vincanine. The indole alkaloid vincanine has a relaxant activity and relaxes the preparations of the rat aorta, previously contracted with a solution of hyperpotassium and phenylephrine.