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Endothelial independence of myogenic response in isolated skeletal muscle arterioles
J C Falcone1, M J Davis, G A Meininger
1Department of Medical Physiology, College of Medicine, Texas A & M University, College Station 77843.
Insights
The endothelium does not influence the myogenic response or spontaneous tone in skeletal muscle arterioles. Studies show that removing the endothelium abolished dilation to acetylcholine but not adenosine.
Area of Science:
- Physiology
- Vascular Biology
- Skeletal Muscle Research
Background:
- The myogenic response is crucial for regulating blood flow in skeletal muscle arterioles.
- The role of the endothelium in mediating this response remains incompletely understood.
Purpose of the Study:
- To investigate the contribution of the endothelium to the myogenic response and spontaneous tone development in rat cremaster skeletal muscle arterioles.
Main Methods:
- Isolated first-order cremaster muscle arterioles were cannulated for in vitro study.
- Vessels were subjected to pressure changes to assess myogenic responses.
- Endothelium-dependent (acetylcholine) and independent (adenosine) vasodilation were tested before and after endothelial denudation.
Main Results:
- Skeletal muscle arterioles developed spontaneous tone and exhibited myogenic constriction/dilation in response to pressure changes.
- Endothelial denudation abolished vasodilation to acetylcholine but did not affect vasodilation to adenosine.
- Basal tone and pressure-induced responses were not significantly altered after endothelial removal.
Conclusions:
- The endothelium is not responsible for the myogenic activity or spontaneous tone in skeletal muscle arterioles.
- These findings differentiate the mechanisms of myogenic tone from endothelium-mediated vasodilation in these vessels.
Abstract:
The goal of this study was to determine whether the endothelium played a role in the myogenic response of skeletal muscle arterioles. First-order arterioles (n = 15) were isolated from the rat cremaster muscle and cannulated for in vitro study. The development of spontaneous tone reduced the diameter of the isolated arterioles from 166.7 +/- 7.6 microns to 89.2 +/- 7.2 microns. The arterioles were exposed to step changes in intraluminal pressure over a range of 10-170 cmH2O and had no flow through their lumen. The vessels exhibited active constriction to step increases or active dilation to step decreases in pressure (50-150 cmH2O). At 90 cmH2O, arterioles dilated by 89.2 +/- 6.0% in response to the endothelium-dependent vasodilator acetylcholine (10(-6) M; ACh) and 89.6 +/- 10.9% in response to endothelium-independent dilator adenosine (10(-4) M; Ado). The endothelium was physically denuded by rubbing the vessel lumen. After denudation, the arteriolar dilation to ACh was abolished, whereas the dilation to Ado was unaltered. The absence of endothelium was verified by electron microscopy. Basal tone and the response to changes in pressure were not significantly different from endothelium-intact vessels. These studies indicate that the endothelium is not responsible for myogenic activity or development of spontaneous tone in skeletal muscle arterioles.