Contact relationships between vascular smooth muscle cells: an in vivo and in vitro study.

Cell/cell contacts in the intact media of the rat thoracic aorta and inferior vena cava, and in cultured smooth muscle cells from these vessels have been quantified in order to determine whether their density and their type can be correlated with the differences in load at these two sites. The type and number of contacts per 100 microns of cell perimeter and per 100 cells were determined with a semi-automatic image analysis system. In all cases there was a predominance of simple appositions; intermediate junctions, interdigitations, and nexus junctions were less frequently observed. There were more cell contacts of each type in the intact arteries than in the intact veins. In cell cultures, all types of cell contacts were increased but the proportion of load bearing types was reduced.