Calcium entry blockers and myocardial function.
Ca2+ enters myocardial cells through a variety of pathways, including in exchange for Na+; by passive diffusion; through voltage-activated, gated channels; and in exchange for K+, Ca2+ entry through the voltage-activated channels is an essential step in excitation-contraction coupling. It is only this component of Ca2+ transport that is inhibited by the Ca2+ entry blockers. As a group, therefore, these drugs interfere with excitation-contraction coupling in heart but not in skeletal muscle. Accordingly they reduce the energy requirements of the heart. Their inhibitory effect on voltage-activated inward transport of Ca2+ into smooth muscle cells also results in dilation of the coronary vessels, with improvement in coronary perfusion, and of peripheral vessels, with after-load reduction. The resultant action of these drugs in maintaining myocardial energy balance and intracellular Ca2+ homeostasis is therefore complex, and tends toward preservation of myocardial structure and function after episodes of ischemia. Although the Ca2+ entry blockers prevent protein release and preserve ultrastructure in damaged myocardium, this is probably an indirect effect of their ability to impede slow channel transport of Ca2+.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology* / Q000627:therapeutic use; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D003327:Coronary Disease / Q000188:drug therapy; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D009200:Myocardial Contraction / Q000187:drug effects*; D012964:Sodium / Q000502:physiology; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D007473:Ion Channels; D012964:Sodium; D014700:Verapamil; D000252:Calcium-Transporting ATPases; D002118:Calcium