title: ANG II type 1 receptor antagonist irbesartan inhibits coronary angiogenesis stimulated by chronic intermittent hypoxia in neonatal rats.
abstract: Chronic hypoxia has been shown to stimulate myocardial microvascular growth and improve cardiac ischemic tolerance in young and adult rats. The aim of this study was to determine whether the ANG II type 1 receptor (AT(1)) pathway was involved in these processes. Newborn Wistar rats, exposed to chronic intermittent hypoxia (8 h/day) for 10 days, were simultaneously treated with AT(1) receptor blocker irbesartan and compared with untreated animals. The major finding is that chronic hypoxia increased the capillary supply of myocardial tissue, which was even more pronounced in hypertrophied right ventricle, whereas increased arteriolar supply was found only in the left ventricle. This angiogenic response was completely prevented by irbesartan. Moreover, chronic hypoxia improved the postischemic recovery of cardiac contractile function during reperfusion, and this protective effect was also completely abolished by irbesartan. Chronic hypoxia increased the myocardial density of AT(1) but not of ANG II type 2 receptor subtypes, whereas the effect of irbesartan was not significant. The expression of caveolin-1alpha markedly increased in response to chronic hypoxia, and irbesartan prevented this effect. Neither hypoxia nor irbesartan treatment altered the expression of nitric oxide synthase 3, heat shock protein 90, and VEGF. It is concluded that the AT(1) receptor pathway plays an important role in coronary angiogenesis and improved cardiac ischemic tolerance induced in neonatal rats by chronic hypoxia.
authors.affiliation: Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Canada.
authors.forename: Karel
authors.initials: K
authors.lastname: Rakusan
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Chvojkova
authors.forename: Patricia
authors.initials: P
authors.lastname: Oliviero
authors.forename: Ivana
authors.initials: I
authors.lastname: Ostadalova
authors.forename: Frantisek
authors.initials: F
authors.lastname: Kolar
authors.forename: Catherine
authors.initials: C
authors.lastname: Chassagne
authors.forename: Jane-Lise
authors.initials: JL
authors.lastname: Samuel
authors.forename: Bohuslav
authors.initials: B
authors.lastname: Ostadal
mesh_terms: D000531:Altitude; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001160:Arterioles / Q000187:drug effects / Q000502:physiology; D001713:Biphenyl Compounds / Q000494:pharmacology*; D002196:Capillaries / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D005260:Female; D000860:Hypoxia / Q000503:physiopathology*; D000077405:Irbesartan; D008297:Male; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D013777:Tetrazoles / Q000494:pharmacology*
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D001713:Biphenyl Compounds; D013777:Tetrazoles; D000077405:Irbesartan