Isometric biaxial tension of smooth muscle in isolated cylindrical segments of rabbit arteries

Biaxial tension developed in the common carotid and femoral arteries of rabbits by the activation of smooth muscle was determined in vitro using cylindrical segments. While the smooth muscle was stimulated with 10(-5) M norepinephrine, the intraluminal pressure and axial force were measured under isometric conditions, i.e., keeping the diameter and length constant. The development of the active tension in the axial direction was roughly proportional to that in the circumferential direction. The ratio of the axial stress response to the circumferential one was positively correlated to the ratio of the axial stretch to the circumferential one. The axial response was larger than expected from the histological observation that the smooth muscle cells align almost circumferentially. This means that although smooth muscle cells are oriented almost circumferentially, the extracellular matrix transmitted the smooth muscle constriction force not only in the circumferential direction, but also in the longitudinal direction under isometric conditions.