Intercellular contacts in the media of the thoracic aorta of rat fetuses treated with beta-aminopropionitrile.

Beta-aminopropionitrile (BAPN) alters the scleroproteins of the arterial media in a way which permits an increase in the stress (force/unit area) applied to smooth muscle cells at a given pressure. Pregnant Sprague-Dawley rats were treated with BAPN and the thoracic aortas of exposed fetuses were studied by electron microscopy and image analysis. Transmission electron microscopy of the media of the thoracic aorta revealed that the types of intercellular contacts seen in the controls and in the BAPN group were intermediate junctions (IJs), nexus junctions (NJs), simple appositions (SAs), and interdigitations (Ids) as in adult vessels. The BAPN-treated animals showed an increased density of IJs, SAs, and Ids when compared with controls but the NJs demonstrated no change. Load-sensitive intercellular contacts have been considered to be the major route by which stress is applied across cells, and the increased number in the BAPN group probably represents a response of the vessel wall to increased tangential tension.