Mechanics of resting isolated single vascular smooth muscle cells from bovine coronary artery.

The viscoelastic behavior of single resting vascular smooth muscle cells from bovine coronary artery was studied. No maintained passive force could be recorded, even when the cells were stretched to two to four times their initial length; this finding suggests that the smooth muscle cells do not contribute to the parallel elastic component in arterial smooth muscle tissue. The force during stretch of resting arterial cells was proportional to the rate of stretch (which varied between 20 and 60% of the initial length per second). This linear viscous resistance was also found for toad stomach cells when similar stretches were applied. The stress-relaxation curves of the arterial cells could be fitted to the sum of two exponential components (with half-lives of 13.1 and 0.5 s, respectively). As a result of the above findings, a model consisting of two viscoelastic elements in parallel was proposed for a single resting arterial smooth muscle cell. The viscous resistance to stretch of resting cells in a Ca2+-containing solution was not significantly (P greater than 0.01) different from that in a Ca2+-free solution. The same result was obtained for bovine coronary arterial rings. It is concluded that an adequate model for resting arterial smooth muscle should include an intracellular viscous element.