In vivo aortic wall characteristics at the early stage of atherosclerosis in rabbits.
To assess whether vascular responsiveness to alpha-receptor agonist is altered at the early stage of atherosclerosis, in vivo aortic pressure-diameter relationship of the aorta over a wide range of pressures was analyzed before and after the acute administration of alpha-receptor agonist (phenylephrine) in nine hypercholesterolemic fat-fed (7-wk-old) rabbits and eight normal diet-fed (7-wk-old) rabbits. In hypercholesterolemic fat-fed rabbits, there was no major structural change in the aortic wall except fatty streak, despite a marked increase in the level of plasma cholesterol, indicating the early stage of atherosclerosis of the aorta. By using a modified three-element Maxwell model, diastolic stress-strain relationship was computed after applying several assumptions to the actual aortic pressure-diameter relationship. After the intravenous administration of phenylephrine at a rate of 5 micrograms.kg-1.min-1, the stress (ordinate)-strain (abscissa) relationship curves were shifted to the left, indicating the activation of aortic smooth muscle by phenylephrine. The difference between the stress before and after phenylephrine showed a single peak at a certain strain. The peak difference in the stress was smaller in hypercholesterolemic fat-fed rabbits than in normal diet-fed rabbits, indicating the reduction of vascular responsiveness at the early stage of atherosclerosis of the aorta.
Hironaka
K
K
Second Department of Internal Medicine, Yamaguchi University School of Medicine, Japan.
Yano
M
M
Kohno
M
M
Tanigawa
T
T
Obayashi
M
M
Konishi
M
M
Umemoto
S
S
Matsuzaki
M
M
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D001161:Arteriosclerosis / Q000473:pathology* / Q000503:physiopathology*; D002784:Cholesterol / Q000097:blood; D002791:Cholesterol, Dietary; D003971:Diastole / Q000187:drug effects; D004036:Diet, Atherogenic; D004548:Elasticity; D006339:Heart Rate; D006439:Hemodynamics / Q000187:drug effects; D006937:Hypercholesterolemia / Q000473:pathology / Q000503:physiopathology; D008297:Male; D008955:Models, Cardiovascular; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D010656:Phenylephrine / Q000494:pharmacology; D011817:Rabbits; D013314:Stress, Mechanical; D013599:Systole / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D002791:Cholesterol, Dietary; D010656:Phenylephrine; D002784:Cholesterol