Studies on the calcium antagonistic action of tetrandrine: IX. Effects of tetrandrine on contractility of isolated swine coronary artery strips

Abstract

Tetrandrine (Tet) 64 μM and verapamil (Ver) 8.4 μM relaxed the contraction of coronary artery strips. It is reversed by raising the extracellular Ca⁺⁺ from 2.7 to 14.4 mM. Within a certain range (Tet 0. 1 μM 0.1 mM, Ver 1 nM 1 μM) the percentage of relaxation was in proportion to the dose. However, Tet and Ver exert no significant inhibition on the extracellular Ca⁺⁺-dependent contraction induced by norepinephrine (NE). Probably Tet and Ver primarily inhibited the potential-dependent channel (PDC) and prevented the influx of Ca⁺⁺ through PDC.

Tet 10 μM and Ver 0.1 μM also inhibited the release of intracellular Ca⁺⁺ by NE. This shows that Tet and Ver might affect the transport of the intracellular Ca⁺⁺. The relaxant effect of isoproterenol on the coronary strips was not blocked by Tet and Ver. Tet is therefore considered to be different from the β-blocker propranolol but similar to the calcium antagonist Ver.

Keywords

tetrandrine / iproveratril / Ca⁺⁺ channel blockers / high K⁺ / norepinephrine / isoproterenol / swine coronary artery strip

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