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Growth-dependent changes in endothelial factors regulating arteriolar tone.

Authors :
Samora JB
Frisbee JC
Boegehold MA
Source :
American journal of physiology. Heart and circulatory physiology [Am J Physiol Heart Circ Physiol] 2007 Jan; Vol. 292 (1), pp. H207-14. Date of Electronic Publication: 2006 Aug 25.
Publication Year :
2007

Abstract

Previous studies from this laboratory suggest that during maturation, rapid microvascular growth is accompanied by changes in the mechanisms responsible for regulation of tissue blood flow. To further define these changes, we studied isolated gracilis muscle arterioles from weanling ( approximately 25 days) and juvenile ( approximately 44 days) Sprague-Dawley rats to test the hypothesis that endothelial mechanisms for the control of arteriolar tone are altered with growth. Responses to the endothelium-dependent dilator acetylcholine (ACh) were greater in weanling arterioles (WA) than in juvenile arterioles (JA), whereas there were no consistent differences between age groups in arteriolar responses to other endothelium-dependent agonists (A-23187, vascular endothelial growth factor, and simvastatin). Inhibition of nitric oxide synthase (NOS) with N(omega)-nitro-l-arginine methyl ester (l-NAME) attenuated ACh-induced dilation in JA but not in WA. In JA, combined inhibition of NOS and cyclooxygenase (with indomethacin) reduced the dilator responses to ACh and simvastatin by approximately 90% and approximately 70%, respectively, but had no effect in WA. Cytochrome P450 epoxygenase inhibition [with 2-(propargyloxyphenyl) hexanoic acid] had no effect on responses to ACh or simvastatin in either age group. Inhibition of Ca(2+)-activated or ATP-dependent potassium channels (with tetraethylammonium or glibenclamide, respectively) reduced these arteriolar responses in JA but not those in WA. These findings suggest that in fully grown microvascular networks, endothelium-dependent arteriolar dilation is mediated by the combined release of endothelial nitric oxide and vasodilator prostanoids, and in part through activation of Ca(2+)-activated and ATP-dependent potassium channels. However, during earlier microvascular growth, this dilation is mediated by other factors yet to be identified. This may have significant implications for the regulation of tissue perfusion during microvascular development.

Details

Language :
English
ISSN :
0363-6135
Volume :
292
Issue :
1
Database :
MEDLINE
Journal :
American journal of physiology. Heart and circulatory physiology
Publication Type :
Academic Journal
Accession number :
16936004
Full Text :
https://doi.org/10.1152/ajpheart.00677.2006