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Different electrical responses to vasoactive agonists in morphologically distinct smooth muscle cell types
C B Neylon1, P V Avdonin, R J Dilley
1Baker Medical Research Institute, Prahran, Victoria, Australia.
Circulation Research
|October 1, 1994
Summary
Vascular smooth muscle cells (SMCs) exhibit distinct ionic responses to vasoactive stimuli. Elongated SMCs depolarize, while epithelial-like SMCs hyperpolarize due to calcium-activated potassium channels.
Area of Science:
- Vascular biology
- Cell physiology
Background:
- Vascular smooth muscle cells (SMCs) display heterogeneity in morphology and function.
- Two predominant SMC populations exist in adult rat arteries: elongated bipolar and epithelial-like cells.
Purpose of the Study:
- To investigate the differential ionic responses of elongated and epithelial-like SMCs to vasoactive stimuli.
- To elucidate the mechanisms underlying membrane potential changes in these distinct SMC populations.
Main Methods:
- Isolation of SMC populations through multiple subcultures.
- Measurement of intracellular sodium ([Na+]i) and calcium ([Ca2+]i) using SBFI and fura 2.
- Assessment of membrane potential changes with the fluorescent probe bis-oxonol.
Main Results:
- Elongated SMCs depolarized upon stimulation with endothelin 1, alpha-thrombin, or arginine vasopressin, driven by Na+ and Ca2+ influx.
- Epithelial-like SMCs exhibited hyperpolarization, mediated by charybdotoxin-sensitive Ca2+-activated K+ channels.
- Hyperpolarization in epithelial-like SMCs was abolished by calcium chelation, revealing a small depolarization.
Conclusions:
- Distinct SMC populations possess unique electrophysiological properties and responses to vasoactive agents.
- Epithelial-like SMC hyperpolarization is primarily mediated by specific calcium-activated potassium channels.
- Understanding these differential responses is crucial for comprehending vascular tone regulation.