Chronic blockade of endothelin ETA receptors improves flow dependent dilation in resistance arteries of hypertensive rats.
OBJECTIVE
Flow (shear stress)-induced dilation (FD) is attenuated in hypertension. Flow triggers the release by endothelial cells of dilators, such as NO or cyclo-oxygenase (COX) derivatives and constrictor factors such as endothelin-1 (ET-1) which might be involved in several cardiovascular diseases. We hypothesized that ET-1 might play a functional role in FD and participate in the endothelial dysfunction in hypertension.


METHODS
We investigated the effect of chronic treatment with the ETA receptor blocker LU135252 (50 mg/kg/day) for 2 weeks on the dilator response to flow in normotensive (Wistar-Kyoto; WKY) or hypertensive (SHR, n = 7 or 8 per group) rats.


RESULTS
Systolic arterial pressure was not significantly affected by chronic ETA receptor blockade in both strains. In mesenteric resistance arteries (diameter: approximately 100 microns), isolated in vitro, FD was lower and myogenic tone higher in SHR than in WKY rats. Chronic ETA receptor blockade increased FD by 73% (7.5 +/- 1.5 to 13.0 +/- 2.7 microns dilation with a flow-rate of 150 microliters/min) in SHR (no effect in WKY). The participation of NO to FD was increased in SHR and the participation of dilator COX product(s) (blocked by indomethacin 10 mumol/l) to FD was significantly increased in SHR and in WKY. In control rats FD was improved by acute ETA receptor blockade in WKY rats (18.5 +/- 2.0 to 23.2 +/- 1.8 microns dilation to flow-rate of 150 microliters/min) and significantly more in SHR (6.0 +/- 1.8 to 15.1 +/- 1.6 microns). Acetylcholine-induced dilation was also improved by chronic ETA receptor blockade (no effect of an acute blockade). Myogenic and phenylephrine-induced tone were not affected by chronic or acute ETA receptor blockade. The improvement of endothelium-dependent dilation was not related to a change in blood pressure.


CONCLUSIONS
Chronic ETA receptor blockade increased flow-induced dilation in SHR possibly by suppressing flow-induced ETA stimulation and by improving the release of dilator products by the endothelium.
Iglarz
M
M
Institut National de la Santé et de la Recherche Médicale (INSERM) U 141, IFR 6 (Circulation-Lariboisière), Université Paris VII, Hôpital Lariboisière, France.
Matrougui
K
K
Lévy
B I
BI
Henrion
D
D
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D065128:Endothelin Receptor Antagonists; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D010666:Phenylpropionates / Q000494:pharmacology* / Q000627:therapeutic use; D011743:Pyrimidines / Q000494:pharmacology* / Q000627:therapeutic use; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D044022:Receptor, Endothelin A; D012039:Regional Blood Flow; D013314:Stress, Mechanical; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
D016861:Cyclooxygenase Inhibitors; D065128:Endothelin Receptor Antagonists; D004791:Enzyme Inhibitors; D010666:Phenylpropionates; D011743:Pyrimidines; D044022:Receptor, Endothelin A; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; C107831:darusentan; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin