Periadventitial Tissue Research Articles

Endothelin Receptor Heterogeneity; Structure Activity, Autoradiographic and Functional Studies

Radioligand binding studies were used to define the binding constants for inhibition of [125I]endothelin-1 binding by endothelin-1 (ET-1), endothelin-3 (ET-3) and a synthetic analogue of ET-1, [Ala1,3,11,15]ET-1 in rat aorta and cerebellum. The inhibition curves for the three substances were similar in the cerebellum (Ki, ET-1 = ET-3 = [Ala1,3,11,15]ET-1) but differed in the aorta (Ki, ET-1 much less than [Ala1,3, 11,15]ET-1) with the ET-3 inhibition curves being biphasic, indicating binding to two sites. In functional studies in the aorta, in contrast to findings in the cerebellum, [Ala1,3,11,15]ET-1 was inactive and ET-3 was a partial agonist. These findings support the idea of heterogeneity of endothelin receptors. Autoradiographic studies were performed to identify the cellular localisation of endothelin-1 receptors in the two tissues. In the aorta binding was to all elements of the vasculature including the endothelium, smooth muscle, periadventitial connective tissue and nerves. In the cerebellum binding sites were located predominantly over the neuronal elements of the granular cell layer. The cellular localisation of the high and low affinity sites for ET-3, and the functional significance of the high affinity binding site for ET-3, remain to be determined.

Angiolathyrism: III. Vasa vasorum in experimental dissecting aortic aneurysm

In order to study the pathogenesis of dissecting aortic aneurysm, an attempt was made to demonstrate aortic medial vasa vasorum by infusion of India ink into 25 weanling rats that had been administered β-aminopropionitrile fumarate for as long as 30 days. More than half of the rats developed gross or microscopic dissecting aneurysms of the aorta, with the frequent occurrence of hemothorax due to rupture. India ink was present in the dissected lumen of the aortic wall but not within intact portions of the media. Capillary networks containing India ink were noted in periadventitial and adventitial layers and in periadventitial granulation tissue covering dissection, but were not found within the media. Infusion of India ink in 18 normal rats showed abundant capillary networks in periadventitial and adventitial layers but failed to reveal capillary vascular structure within the media of aorta. The results of this study indicate that in experimental dissecting aortic aneurysm in rats induced by β-aminopropionitrile fumarate the vasa vasorum do not play a role in its pathogenesis.