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The specialized conduction system of the rat heart was studied by light and electron microscopy at various periods following vagotomy. The dynamics of tissue and cellular alterations is described. Variegation of the cellular reactions at all the postdenervation periods for all the conduction system parts and for all types o specialized cardiomyocytes was revealed.
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Intracardiac electrophysiologic studies of the sinus node and conductive system of the heart were carried out in 51 patients with ventricular allorhythmias. In half of the cases, ventricular allorhythmias occurred in patients with impaired sinus node operation and abnormal atrioventricular impulse conduction. It is suggested that anti-arrhythmic drugs associated with adverse chrono- and dromotropic effects should be used with caution.
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The present investigation was designed to elucidate which role the sympathetic nerves play in the immunoexpression of atrial natriuretic peptide in the cardiac conduction system of the rat. In order to destroy the cardiac sympathetic nerve terminals, both surgical and chemical sympathectomy were performed. By use of immunohistochemical and radioimmunoassay techniques, the immunoreactivity and level of atrial natriuretic peptide in the conduction system and in the cardiac myocardium were determined. In contrast to the low degree of immunoreaction for atrial natriuretic peptide seen in control rats, the sympathectomized rats exhibited pronounced immunoreactivity for atrial natriuretic peptide in the atrioventricular bundle and bundle branches, which normally have high numbers of sympathetic nerve fibres. On the other hand, in the peripheral parts of the conduction system, where there are ordinarily few sympathetic nerve fibres, the degree of immunoreaction was unchanged. The quantitative measurements also showed that the entire ventricles, including the conduction system, contained increased levels of atrial natriuretic peptide in the treated hearts. The present study shows that destruction of the sympathetic nervous system leads to an increased level of atrial natriuretic peptide in the Purkinje fibres of bundle branches, which thus seem to have a dormant capacity for synthesis of this peptide. The results provide new evidence about the change in atrial natriuretic peptide levels that occurs when sympathetic innervation is altered.
We characterized angiotensin II receptor subtypes in the conduction system of the rat heart using quantitative autoradiography. In both the sinoatrial and atrioventricular nodes, binding could be totally displaced by losartan, and was insensitive to PD 123177, indicating that angiotensin II receptors in the conduction system of the rat heart belong to the AT1 subtype. Angiotensin AT1 receptors could play a direct role in the regulation of the heart chronotropic properties.
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In 112 preparations of hearts from persons at the age of 18-87 years by means of the preparation method (77 hearts) and in histograms stained after Van Gieson, Mallory, Heidenhain and Masson (35 hearts), certain new data on the cardiac conduction system (CCS) have been obtained. A number of fasciculi connected with the sinuatrial and atrioventricular nodes have been revealed. The atrioventricular part of the CCS, as a more ancient one, is characterized by a more constant structure and topography. The sinuatrial part of the CCS, being phylogenetically younger, has a high degree of individual anatomical changeability.
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