Large artery remodeling during aging: biaxial passive and active stiffness.
To examine arterial mechanical changes during aging, pressure-radius and axial force-radius curves were measured in vivo in carotid arteries from 6- and 23-month-old Brown Norway X Fischer 344 rats. Incremental passive circumferential stiffness (measured at 50, 100, and 200 mm Hg) was higher (P<0.01) in the 23- compared with the 6-month-old rats (14.02+/-1.23 versus 6.58+/-1.51; 2.68+/-0.56 versus 0.99+/-0.34; 1.10+/-0.24 versus 0.69+/-0.15 dyne/mm2x10(3), respectively). Incremental passive axial stiffness was increased (P<0.01) in the 23- compared with the 6-month-old rats (7.95+/-0.70 versus 4.24+/-0.81; 1.91+/-0.10 versus 0.61+/-0.16; 0.58+/-0.09 versus 0.36+/-0.06 dyne/mm2x10(3), respectively). Active incremental circumferential arterial stiffness at 100 and 200 mm Hg was increased (P<0.01) in the older rats. In 6-month-old rats, activation of vascular smooth muscle enhanced (P<0.01) the incremental circumferential and axial stiffness measured at 200 mm Hg. In 23-month-old rats, only active incremental stiffness was increased (P<0.01) at 200 mm Hg. Aging increased (P<0.05) media thickness, collagen content, and the collagen/elastin ratio by 12%, 21%, and 38%, respectively. Elastin density and the number of smooth muscle cell nuclei were decreased by 20% and 31%, respectively, with aging. Thus, structural alterations that occur with aging are associated with changes in both active and passive stiffness. Vascular smooth muscle tone modulates arterial wall anisotropy differently during aging.
Gaballa
M A
MA
From the Department of Internal Medicine, Veterans Administration Medical Center and University Heart Center, Aerospace and Mechanical Engineering, University of Arizona, Tucson, Ariz, USA.
Jacob
C T
CT
Raya
T E
TE
Liu
J
J
Simon
B
B
Goldman
S
S
D000375:Aging / Q000502:physiology*; D000818:Animals; D001158:Arteries / Q000502:physiology*; D002339:Carotid Arteries / Q000502:physiology; D006439:Hemodynamics; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009638:Norepinephrine / Q000378:metabolism; D051381:Rats; D014661:Vasoconstriction; D014662:Vasoconstrictor Agents / Q000378:metabolism
D014662:Vasoconstrictor Agents; D009638:Norepinephrine