Mechanical properties of rat middle cerebral arteries with and without myogenic tone.
The inner diameter and wall thickness of rat middle cerebral arteries (MCAs) were measured in vitro in both a pressure-induced, myogenically-active state and a drug-induced, passive state to quantify active and passive mechanical behavior. Elasticity parameters from the literature (stiffness derived from an exponential pressure-diameter relationship, beta, and elasticity in response to an increment in pressure, Einc-p) and a novel elasticity parameter in response to smooth muscle cell (SMC) activation, Einc-a, were calculated. beta for all passive MCAs was 9.11 +/- 1.07 but could not be calculated for active vessels. The incremental stiffness increased significantly with pressure in passive vessels; Einc-p (10(6) dynes/cm2) increased from 5.6 +/- 0.5 at 75 mmHg to 14.7 +/- 2.4 at 125 mmHg, (p < 0.05). In active vessels, Einc-p (10(6) dynes/cm2) remained relatively constant (5.5 +/- 2.4 at 75 mmHg and 6.2 +/- 1.0 at 125 mmHg). Einc-a (10(6) dynes/cm2) increased significantly with pressure (from 15.1 +/- 2.3 at 75 mmHg to 49.4 +/- 12.6 at 125 mmHg, p < 0.001), indicating a greater contribution of SMC activity to vessel wall stiffness at higher pressures.
Coulson
Rebecca J
RJ
Mechanical Engineering Department, University of Vermont, Burlington, VT 05405, USA.
Cipolla
Marilyn J
MJ
Vitullo
Lisa
L
Chesler
Naomi C
NC
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D003198:Computer Simulation; D004548:Elasticity; D066298:In Vitro Techniques; D008297:Male; D020768:Middle Cerebral Artery / Q000502:physiology*; D008955:Models, Cardiovascular; D009119:Muscle Contraction / Q000502:physiology*; D009129:Muscle Tonus / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar