Related Experiment Video
Updated: Aug 9, 2026

Impact of Intracardiac Neurons on Cardiac Electrophysiology and Arrhythmogenesis in an Ex Vivo Langendorff System
Published on: May 22, 2018
Effects of isoproterenol on the dense core and perigranular membrane of atrial specific granules
Abstract:
Following subcutaneous injections of isoproterenol hydrochloride (ISO), atrial cells present a large number of partly degranulated or completely clear "specific granules" enclosed by an intact membrane. Such profiles were never encountered in normal controls and might suggest ISO-induced release of a secretory product. Permeability of perigranular membrane was tested using the extracellular macromolecular tracer horseradish peroxidase (HRP). Reaction product was entirely absent within granules of atrial cells in which the sarcolemma was made permeable to HRP molecules by the ISO injections. This seemed to be the case even in heavily labelled cells in which the peroxidase had penetrated the mitochondrial membranes. In atrial cells impermeable to the tracer, the specific granules closely apposed to the sarcolemma were always HRP-negative. The release mechanism of a possible secretory substance from the specific granules is discussed.
Related Concept Videos
G-Protein Gated Ion Channels
Sensory organs,...
Adrenergic Receptors: β Subtype
Isoprenaline > Adrenaline > Noradrenaline
Neurotransmitter binding to these receptors causes activation of adenylyl cyclase resulting in increased concentrations of cAMP and modulation of calcium ion channels within the cell. They are further classified into β1, β2, and β3 subtypes.
β1-adrenoceptors: β1-adrenoceptors have equal affinities for...
Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers
Heart Failure Drugs: Inotropic Agents
Conduction System of the Heart
The pacemaker cells are located in two primary nodes: the sinoatrial (SA) node and the atrioventricular (AV) node. The SA node pacemaker cells can autonomously depolarize, triggering an action potential that leads to the...
Conduction System of the Heart
This system relies on the unique properties of nodal and Purkinje cells:...

