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Role of Vascular Heme Oxygenase in Reduced Myogenic Reactivity Following Chronic Hypoxia
Author(s) -
NAIK JAY S.,
WALKER BENJIMEN R.
Publication year - 2006
Publication title -
microcirculation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.793
H-Index - 83
eISSN - 1549-8719
pISSN - 1073-9688
DOI - 10.1080/10739680500466301
Subject(s) - heme oxygenase , epoxygenase , chemistry , myogenic contraction , hypoxia (environmental) , mesenteric arteries , vascular smooth muscle , heme , endocrinology , vasoconstriction , medicine , anatomy , artery , biochemistry , cytochrome p450 , enzyme , oxygen , smooth muscle , organic chemistry
Objective: Exposure to chronic hypoxia (CH) results in a persistent endothelium‐dependent vascular smooth muscle hyperpolarization that diminishes vasoconstrictor reactivity. Experiments were performed to test the hypothesis that products of both cytochrome P450 epoxygenase (CYP) and heme oxygenase (HO) are required for the persistent diminished myogenic reactivity following CH. Methods: The authors examined myogenic responses of mesenteric arteries isolated from control and CH (48 h; P B = 380 mmHg) rats in the presence of a HO inhibitor (zinc protoporphyrin IX; ZnPPIX) or combined HO and CYP epoxygenase inhibition (sulfaphenazole). Arteries were isolated and cannulated and the vascular smooth muscle was loaded with the Ca 2 + indicator Fura‐2. Results: Control vessels maintained their internal diameter in response to step increases in intraluminal pressure, whereas arteries from CH animals passively distended. ZnPPIX augmented myogenic reactivity and [Ca 2 + ] in arteries from CH animals. Combined administration of sulfaphenazole and ZnPPIX did not have an additional effect compared to ZnPPIX alone. Myogenic reactivity in control vessels was not altered by ZnPPIX or ZnPPIX + sulfaphenazole. Conclusions: HO appears to play a role in regulating myogenic reactivity following CH. Furthermore, these data suggest that products of HO and CYP are both required for the observed attenuation in vasoreactivity following CH.