The effect of smooth muscle activation on the mechanical properties of pig carotid arteries.
The contractile properties and the effect of contraction on the mechanical properties of noradrenaline (0.5 micrograms/ml) activated smooth muscle of cylindrical segments of porcine carotid arteries were studied in vitro under quasi-static pressure loading. Maximum tangential isometric stress developing in the vessel wall was 4.4 +/- 0.6 X 10(5) dyn/cm2. Incremental elastic modules of activated smooth muscle, calculated for total wall cross sectional area, was 4.6 +/- 2.7 X 10(6) dyn/cm2, whereas the value computed for estimated smooth muscle thickness was 9.8 +/- 14.8 X 10(6) dyn/cm2. During smooth muscle activation maximum increase of strain-energy density of the vessel wall was 6.8 +/- 1.2 X 10(4) dyn/cm2 under isometric conditions and 25 +/- 3% increase occurred under isobaric conditions. Isobaric diameter response was only 2--4% in the physiological pressure range (100--150 mmHg) while the incremental elastic modulus decreased by 40 +/- 3% and distensibility increased by 80 +/- 10% under isobaric conditions. Smooth muscle activation induced a 19 +/- 2% maximum decrease of characteristic impedance, and a rather a uniform 14--15% decrease in the impedance was observed in the 100--150 mmHg pressure range. The obtained results show that the control of distensibility and elastic modulus in smooth muscle is most efficient in the physiological pressure range under in vitro conditions. It is assumed that in vivo in addition to vascular diameter the most important controlled parameters are the distensibility and characteristic impedance of the large arteries.
D000818:Animals; D001696:Biomechanical Phenomena; D002339:Carotid Arteries / Q000502:physiology; D006439:Hemodynamics / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D013552:Swine
D009638:Norepinephrine