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Published on: August 16, 2016
An intrinsic adrenergic system in mammalian heart
M H Huang1, D S Friend, M E Sunday
1Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA.
Insights
Researchers discovered a new intrinsic cardiac adrenergic (ICA) cell type in the heart. These cells produce catecholamines and influence heart rate independently of the sympathetic nervous system.
Area of Science:
- Cardiology
- Cell Biology
- Neuroscience
Background:
- The heart's regulation involves complex signaling systems.
- The role of intrinsic cardiac cells in cardiac regulation is not fully understood.
Purpose of the Study:
- To identify and characterize a novel intrinsic cardiac adrenergic (ICA) cell type.
- To investigate the functional role of ICA cells in cardiac regulation.
Main Methods:
- Northern and Western blot analyses for enzyme expression.
- Radioenzymatic catecholamine assays.
- Electron microscopy for cellular morphology.
- In vitro studies on neonatal rat cardiac myocytes.
Main Results:
- Identified a new ICA cell type in rodent and human hearts.
- ICA cells express catecholamine biosynthesis enzymes.
- ICA cells release endogenous catecholamines affecting heart rate.
- ICA cells are present in human fetal hearts before sympathetic innervation.
Conclusions:
- ICA cells represent a distinct signaling system within the heart.
- This system appears to regulate cardiac function independently of sympathetic innervation.
Abstract:
We have identified a previously undescribed intrinsic cardiac adrenergic (ICA) cell type in rodent and human heart. Northern and Western blot analyses demonstrated that ICA cell isolates contain mRNA and protein of enzymes involved in catecholamine biosynthesis. Radioenzymatic catecholamine assays also revealed that the catecholamine profile of adult rat ICA cell isolates differed from that of sympathetic neurons. Unlike sympathetic neuronal cells, isolated ICA cells have abundant clear vesicles on electron microscopy. Endogenous norepinephrine and epinephrine constitutively released by ICA cells in vitro affect the spontaneous beating rate of neonatal rat cardiac myocytes in culture. Finally, ICA cells could be identified in human fetal hearts at a developmental stage before sympathetic innervation of the heart has been documented to occur. These findings support the concept that these cells constitute an ICA signaling system capable of participating in cardiac regulation that appears to be independent of sympathetic innervation.
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