Interaction of angiotensin II with functional smooth muscle cells in culture

In this study we report on the characterization of a highly enriched population of cultured vascular smooth muscle cells (SMC) prepared from collagenase-treated medial layer explant outgrowths of rabbit aortae. Studies done on cells from first passage explant outgrowths showed that the cells retain the fine structural features of vascular SMC in situ, can be immunostained with anti-smooth muscle myosin IgG, and bind [125I]angiotensin II (ANG II) in a specific and saturable manner with an apparent Kd of 1 nM. Addition of ANG II (0.1 microM) to the cultures causes obvious shape changes and retraction of cell processes. Electron microscopic autoradiography of cells labeled with [125I]ANG II show that the initial site of interaction of ANG II with the SMC is the plasma membrane. The distribution of ANG II receptors among cells in the population was studied using light microscopic autoradiography. The autoradiographical grain density varied among cells in the population ranging from cells that were heavily labeled to those that possessed virtually no label. These data imply that the expression of ANG II receptors may be limited to a certain progeny within the cell population or is a function of their stage within the cell cycle.