Endothelin type A receptor antagonist normalizes blood pressure in rats exposed to eucapnic intermittent hypoxia.
We have reported that eucapnic intermittent hypoxia (E-IH) causes systemic hypertension, elevates plasma endothelin 1 (ET-1) levels, and augments vascular reactivity to ET-1 and that a nonspecific ET-1 receptor antagonist acutely lowers blood pressure in E-IH-exposed rats. However, the effect of chronic ET-1 receptor inhibition has not been evaluated, and the ET receptor subtype mediating the vascular effects has not been established. We hypothesized that E-IH causes systemic hypertension through the increased ET-1 activation of vascular ET type A (ET(A)) receptors. We found that mean arterial pressure (MAP) increased after 14 days of 7 h/day E-IH exposure (109 +/- 2 to 137 +/- 4 mmHg; P < 0.005) but did not change in sham-exposed rats. The ET(A) receptor antagonist BQ-123 (10 to 1,000 nmol/kg iv) acutely decreased MAP dose dependently in conscious E-IH but not sham rats, and continuous infusion of BQ-123 (100 nmol.kg(-1).day(-1) sc for 14 days) prevented E-IH-induced increases in MAP. ET-1-induced constriction was augmented in small mesenteric arteries from rats exposed 14 days to E-IH compared with those from sham rats. Constriction was blocked by the ET(A) receptor antagonist BQ-123 (10 microM) but not by the ET type B (ET(B)) receptor antagonist BQ-788 (100 microM). ET(A) receptor mRNA content was greater in renal medulla and coronary arteries from E-IH rats. ET(B) receptor mRNA was not different in any tissues examined, whereas ET-1 mRNA was increased in the heart and in the renal medulla. Thus augmented ET-1-dependent vasoconstriction via vascular ET(A) receptors appears to elevate blood pressure in E-IH-exposed rats.
Allahdadi
Kyan J
KJ
Dept. of Cell Biology and Physiology, Univ. of New Mexico Health Sciences Ctr., Albuquerque, NM 87131, USA.
Cherng
Tom W
TW
Pai
Hemanth
H
Silva
Ana Q
AQ
Walker
Benjimen R
BR
Nelin
Leif D
LD
Kanagy
Nancy L
NL
D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D003331:Coronary Vessels / Q000187:drug effects / Q000503:physiopathology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D065130:Endothelin A Receptor Antagonists; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1 / Q000378:metabolism*; D006973:Hypertension / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D000860:Hypoxia / Q000150:complications / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D007263:Infusions, Parenteral; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000503:physiopathology; D009842:Oligopeptides / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000008:administration & dosage / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044022:Receptor, Endothelin A / Q000235:genetics / Q000378:metabolism; D012077:Renal Artery / Q000187:drug effects / Q000503:physiopathology; D013997:Time Factors; D014661:Vasoconstriction / Q000187:drug effects
D000959:Antihypertensive Agents; D065130:Endothelin A Receptor Antagonists; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1; D009842:Oligopeptides; D010456:Peptides, Cyclic; D010880:Piperidines; D044022:Receptor, Endothelin A; C086539:BQ 788; C072247:cyclo(Trp-Asp-Pro-Val-Leu)