Cell to stroma contacts in the tunica media of the hypertensive rat thoracic aorta.

The variation in mechanical stress to which the aortic wall is subjected requires that forces be transmitted between its components by means of relatively strong but compliant attachments. We have used transmission electron microscopy in order to study the cell to stroma contacts (smooth muscle cell-elastic fiber contact) in the tunica media of normotensive and hypertensive aortas of Sprague-Dawley rats. Hypertension was produced with a silver clip positioned around the left renal artery and the vessels were fixed by intravital perfusion at normal and elevated pressure. In ultrathin sections, the density of cell to stroma contacts per 100 microns cell perimeter and per 100 cell profiles were determined using an image analysis computer. In the hypertensive group the density of cell to stroma contacts fell considerably when compared with the control group. This research provides insights into the conditions under which high blood pressure may produce medial injuries and, perhaps, be a factor in the precipitation of dissections.