Studies on the calcium antagonistic action of tetrandrine: V. Effects of tetrandrine, verapamil and propranolol on contractility and cAMP level of isolated rabbit left atria

Abstract

A comparison of the effects of tetrandrine (Tet), verapamil (Ver) and propranolol (Pro) on cAMP level and force of contraction was made on isolated left atrial strips of rabbits.

Pro antagonized the increase of cAMP and force of contraction caused by isoproterenol, but Tet and Ver did not. This indicates that Tet and Ver do not react with β-adrenoceptors.

These results are in consistence with those of our previous experiments on cat papillary muscle and rabbit right atrium and further support that Tet may be a Ca⁺⁺-antagonist, not a β-receptor blocker.

Keywords

tetrandrine / Ca⁺⁺-antagonist / iproveratril / propranolol / cAMP / atrial strips of rabbits

References

[1] JimMW, et al. . Studies on the calcium antagonistic action of tetrandrine: I. Effect of tetrandrine on positive inotropic action of isoproterenol and Ca⁺⁺ and on excitation-contraction coupling in isolated cat papillary muscles. Acta Acad Med Wuhan, 1982, 2(4): 223-28

[2] FangDC, et al. . Studies on the calcium antagonistic action of tetrandrine: IV. Effects of tetrandrine on isoproterenol and calcium-mediated positive chronotropic action in isolated rabbit atria. Acta Acad Med Wuhan, 1984, 4(1): 8-11

[3] LevyJV. SchwartzA. Isolated Atrial Preparations. Methods in Pharmacology, 19711st ed.New York, Meredith Corp: 77-104

[4] WatanabeAM, BeschHR. Subcellular myocardial effects of verapamil and D600: Comparison with propranolol. J Pharmacol Exp Ther, 1974, 191(2): 241-51

[5] EndohM, NakamuraM. Effects of 8-S-benzyl cyclic AMP on mechanical characteristics and cAMP levels of the canine ventricular myocardium. Eur J Pharmacol, 1980, 62(1): 63-72

[6] SchümannHJ, et al. . The time course of effects of B and adrenoceptor stimulation by isoprenaline and methoxamine on the contractile force and cAMP level of the isolated rabbit papillary muscle Naunyn-Schmiedebergs. Arch Pharmacol, 1975, 289(3): 291-302

[7] YaoWX, et al. . Studies on the calcium antagonistic action of tetrandrine: I. Effects of tetrandrine on cat papillary muscle. Acta Acad Med Wuhan, 1982, 2(1): i51-54