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Results for “Heart Atria”

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At least 37 records · Page 2Linked to original sources
PubMed1992

[The effect increased choline levels on the synthesis and release of acetylcholine in heart atria in white rats].

The paper addresses the problem of (1) the relationship of choline in extracellular fluid and acetylcholine (ACh) synthesis in chambers of the heart of white rats, and (2) the possibility of physiological involvement of this ACh in the control of cardiac activity. Within 60 min after s.c. administration of choline in the dose of 300 mg/kg body weight the ACh content rose to 136% of the control value in isolated heart chambers and after administration of 400 mg/kg body weight to 159% of the control value. Increased ACh synthesis failed to affect the heart rate, nor did it increase the tonic effect of vagus innervation of the heart. Excessive ACh could however be released by electric transmural stimulation of isolated heart chambers as well as by potassium depolarization. The release depended on the presence of calcium ions. The obtained results demonstrate that an increase in the level of choline in extracellular fluid results in increased ACh synthesis in nerve terminals. Enhanced release of this ACh is a precondition for high choline levels to induce an increase in parasympathetic control of cardiac function.

Acetylcholine↗
PubMed1984

Secretin-induced changes in rate, contractility and adenylate cyclase activity in rat heart atria.

Secretin stimulated adenylate cyclase activity in crude membrane preparations from right and left rat atria, when tested in the presence of the potentiating activator forskolin. Its maximal effect on adenylate cyclase activity was greater in the right atrium than in the left atrium but the peptide efficiency was lower, in both atria, than that of D,L-isoproterenol. Secretin stimulated the rate of contraction of the spontaneously beating right atrium, but less efficiently than D,L-isoproterenol. Although this positive chronotropic action of secretin was inhibited by D,L-propranolol, it was probably not mediated by the release of endogenous catecholamines as: a) the inhibitory effects of D- and L-propranolol were similar and b) the efficiency of secretin on the in vitro beating of right atrium was the same in control and reserpinized rats. Secretin stimulated the force of contraction of spontaneously beating right atrium, even in the presence of propranolol, i.e. when the chronotropic effect of secretin was abolished. The hormone exerted also a positive inotropic effect on the electrically stimulated rat atrium. This effect was blocked neither by tetrodotoxin nor by propranolol. When comparing the dose-effect curves of secretin and D,L-isoproterenol on adenylate cyclase activation on the one hand, and on the stimulation of rate and contractility on the other hand, it is tempting to suggest that cyclic AMP might be involved in the modulation by secretin of the mechanical properties of rat atria.

Adenylyl Cyclases↗
PubMedDate not supplied

[Action potentials of the heart atria and ventricles of Rana temporaria frogs and Cyprinus carpio carp].

Using microelectrode technique, studies have been made on electrophysiological indices (amplitude of AP, amplitude of the plateau, latent period of AP, duration of maximal depolarization, duration of repolarization at different levels) of cells of isolated atrium and ventricles of the carp during both the spontaneous activity and electrical stimulation. The obtained amplitude-temporal parameters were compared to those of the heart in the frog R. temporaria. It was found that the amplitude of AP, the amplitude of the plateau and the duration of the latent period of AP in both the atrium and ventricles of the carp significantly (p less than 0.01) differ from the corresponding indices of the frog. On the contrary, the duration of maximal depolarization and repolarization in cells from homologous parts of the heart is very close in the species investigated.

Action Potentials↗
PubMed1996

Immunocytochemical localization of rH1 sodium channel in adult rat heart atria and ventricle. Presence in terminal intercalated disks.

BACKGROUND: Of the five sodium channel subtypes expressed in cardiac tissues, the rat (rH1) and human (hH1) isoforms are thought to be the predominant subtypes on the basis of heterologous expression studies. In this study, subtype-specific antibodies and immunocytochemistry were used to confirm protein expression and to localize rH1 protein in cardiac tissues. METHODS AND RESULTS: Subtype-specific antibodies immunolabeled adult rat heart tissue in a manner identical to that obtained with subtype-nonselective antibodies. All antibodies specifically bound to the surface and t-tubular systems of atrial and ventricular muscle cells. Cytoplasmic labeling, reflecting nascent sodium channels or cytoplasmic stores of sodium channel protein, was apparent. Most notably, all antibodies also specifically labeled the subset of intercalated disks located at the ends but not the sides of adjacent ventricular muscle cells. CONCLUSIONS: rH1 is the predominant subtype expressed on rat atrial and ventricular muscle cells. rH1 protein localization in surface and t-tubular membranes is consistent with its proposed role in coordinating membrane depolarization along the length and deep within cardiac muscle cells. rH1 protein localization in terminal intercalated disks suggests that sodium channels may also act as a localized voltage-dependent current amplifier, raising the safety margin for conduction; they also may contribute to anisotropic or saltatory conduction in cardiac tissues. These electrophysiological properties would be particularly important under conditions of altered, channel function resulting from ion channel gene defects (e.g., long QT syndrome), antiarrhythmic drug therapy, ischemia, or other heart diseases by influencing the electrophysiological substrate for ventricular tachyarrhythmias.

Amino Acid Sequence↗
PubMed1989

[Differences in the activity of enzymes associated with energy metabolism in the heart atria and ventricles in children].

Tissue specimens from the right atrium and ventricle of the same heart were obtained during surgery in 45 children operated on account of congenital heart disease (tetralogy of Fallot and ventricular septal defect). Significant differences were found in the enzyme activities between the atrial and ventricular musculature. The activities of enzymes associated with aerobic metabolism (citrate synthase, malate dehydrogenase, with lactate metabolism) lactate dehydrogenase (and the fatty acid oxidation) hydroxyacyl-SoA-dehydrogenase) were significantly higher in the ventricular musculature. Hexokinase, the enzyme responsible for glucose phosphorylation was on the other hand, significantly higher in the atria. From this ensues that the right ventricle can utilize and oxidize to a full extent all main nutrients (fatty acids, glucose and lactate), while the right atrium utilizes above all glucose. These atrio-ventricular differences do not depend on the type of the congenital heart disease and it may be assumed that they exist also in healthy subjects.

Adolescent↗