Vascular smooth muscle: quantitation of cell thickness in the wall of arterioles in the living animal in situ.

The wall of microarterial vessels, in the living animal in situ, was examined at magnification up to x 6500 on the television screen. The optical resolution af the cell components of the wall was sufficiently clear to permit image formation and splitting for permanent recording and quantitation. Thickness of single smooth muscle cells at rest was estimated to be 2.08 microns (S.D. +/- 0.24 micron) and 2.78 microns (S.D. +/- 0.59 micron) by two different approaches. Changes in cell thickness during activity were also recorded and quantitated.