In addition to stretch-activated channels (SAC) that respond to purely mechanical stimuli (e.g. Chapter 2), the heart possesses voltage- and ligand-gated channels and ion transporters that are modulated by cell volume. Volume-activated channels (VAC) and SAC are distinguished empirically by the nature of the stimulus. Both stimuli alter membrane tension and cytoskeletal stress and trigger overlapping signalling cascades; consequently the distinction between VAC and SAC is not absolute.
Insights into the role of VAC in the heart are still emerging. Myocyte volume increases acutely with ischaemia/reperfusion, chronically with hypertrophy and remodelling and is affected by disease-induced alterations of serum osmolarity. Atrial natriuretic peptide, autonomic stimulation and cardiovascular agents, including nitrates and diuretics, also regulate cell volume. Therefore, volume-sensitive channels and transporters contribute in multiple settings.
Chapter. 6613 words. Illustrated.
Subjects: Cardiovascular Medicine
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