When smooth muscle cells in the tunica media of the blood vessel wall contract, the vessel lumen decreases in diameter and the resistance to blood flow increases. Since the cells do not physically contact one another, they must be mechanically linked through the extracellular matrix in order to efficiently transmit force. The connections between the fibrous, force transmitting components of the matrix and the cell surface have not been extensive or comparatively studied in vascular smooth muscle. The goal of this proposal is to produce immunocytochemical, morphometric, and three-dimensional data on the relationship between the cell surface and the extracellular matrix in arterial smooth muscle. Information will be obtained for three classes of arteries which have been induced to contract or relax with pharmacological agents. The results of these investigations will provide an essential framework for understanding the structural linkages underlying force transmission in normal and diseased vascular smooth muscle.