Effect of AT1 receptor blockade on intermittent hypoxia-induced endothelial dysfunction.
Chronic intermittent hypoxia (CIH) raises arterial pressure, impairs vasodilator responsiveness, and increases circulating angiotensin II (Ang II); however, the role of Ang II in CIH-induced vascular dysfunction is unknown. Rats were exposed to CIH or room air (NORM), and a subset of these animals was treated with losartan (Los) during the exposure period. After 28 days, vasodilatory responses to acetylcholine or nitroprusside were measured in isolated gracilis arteries. Superoxide levels and Ang II receptor protein expression were measured in saphenous arteries. After 28 days, arterial pressure was increased and acetylcholine-induced vasodilation was blunted in CIH vs. NORM, and this was prevented by Los. Responses to nitroprusside and superoxide levels did not differ between CIH and NORM. Expression of AT(2)R was decreased and the AT(1)R:AT(2)R ratio was increased in CIH vs. NORM, but this was unaffected by Los. These results indicate that the blood pressure elevation and endothelial dysfunction associated with CIH is dependent, at least in part, on RAS signaling.
John Rankin Laboratory of Pulmonary Medicine, University of Wisconsin, Madison, WI 53706-1532, USA. nmarcus@unmc.edu
Noah J
NJ
Marcus
Nathan R
NR
Philippi
Cynthia E
CE
Bird
Yu-Long
YL
Li
Harold D
HD
Schultz
Barbara J
BJ
Morgan
D000109:Acetylcholine / Q000494:pharmacology; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology*; D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000503:physiopathology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D019808:Losartan / Q000494:pharmacology; D008297:Male; D009599:Nitroprusside / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044140:Receptor, Angiotensin, Type 1 / Q000502:physiology*; D011945:Receptors, Angiotensin / Q000096:biosynthesis; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013481:Superoxides / Q000032:analysis; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
D047228:Angiotensin II Type 1 Receptor Blockers; D044140:Receptor, Angiotensin, Type 1; D011945:Receptors, Angiotensin; D013481:Superoxides; D009599:Nitroprusside; D019808:Losartan; D000109:Acetylcholine