[Effect of calcitonin on the electrical activity of the sinoatrial node and contractile myocardium of homeotherms].

The effect of calcitonin on the AP parameters of different myocardium cells in rabbit and guinea pig is related to different significance of fast and slow flow channels for generation of different AP components. Thus, instead of enhancement of the AP amplitude revealed in the cells of the contractile myocardium of warm--and cold--blooded animals and related to stimulation of Na+ transport via fast Na+ channels, calcitonin induced a decrease in the AP amplitude of the heart pace--maker cells in rabbits. The calcitonin effects proved to be different in actions upon the authentic and the latent pace--maker cells.