Title

Effects of divalent cation ionophore A23187 on cardiac contractile parameters

UMMS Affiliation

Department of Physiology

Date

12-1985

Document Type

Article

Subjects

Acetylcholine; Action Potentials; Ammonium Chloride; Animals; Calcimycin; Calcium; Gallopamil; Guinea Pigs; Histamine; Hydrogen-Ion Concentration; Isoproterenol; Magnesium; Male; Myocardial Contraction; Myocardium; Prostaglandins; Stimulation, Chemical

Disciplines

Physiology

Abstract

The divalent cation ionophore A23187, when added to guinea pig papillary muscle, produced contractile effects that were similar to those produced by isoproterenol or histamine, but the ionophore's effects did not appear to result from the release of endogenous transmitters or prostaglandin production. Optimally effective concentrations of A23187 (6 microM) and isoproterenol (1 microM) more than doubled the peak contractile force and the rates of force development and relaxation and caused a 25% decrease in the duration of the contraction. Both A23187 and isoproterenol decreased the resting tension by approximately 0.15 g and significantly diminished the magnitude of a potassium-induced contracture. The positive inotropic effect of A23187 was prevented by incubating the tissue in calcium-depleted medium and antagonized by D 600, a blocker of sarcolemmal calcium influx, and acetylcholine. The contractile effects of A23187 appear to be related, in part, to its ability to increase the movement of calcium across the sarcolemma electroneutrally, since no change of the action potential occurred. In addition, possible intracellular actions of this ionophore may produce contractile effects that resemble those produced by isoproterenol and that reflect an increased sequestration of calcium within the myocardial cell.

Rights and Permissions

Citation: Am J Physiol. 1985 Dec;249(6 Pt 2):H1195-203.

Related Resources

Link to article in PubMed

PubMed ID

3934987