[Ultrastructure of the pacemaker cells of the sinoatrial node in rats].

Ultrastructure of the cells generating the action potential, specific for the pacemaker of the sinuous-auricular node has been studied. The cells are labelled with lanthanum chloride by means of the registrating microelectrode. Two types of pacemakers are revealed. The cells of one type contain specific auricular granules, while those of the other type do not contain them. The pacemaker-cells of the sinuous-auricular node have some peculiarities in the structure of the contractile apparatus, mitochondria, Golgi complex, intercellular contacts owing to which their morphological identification is possible.