[125I]-ET=1 Binding to Perivascular Nerves of Human Epicardial Coronary Arteries

Further evidence for a role of endothelin-1 (ET-1) in critical limb ischaemia

Critical limb ischaemia (CLI), due to atherosclerotic arterial occlusion, affects over 20,000 people per year in the United Kingdom with many facing lower limb amputation and early death. A role for endothelin-1 (ET-1) in atherosclerosis is well-established and increased circulating and tissue levels of this peptide have been detected in patients with CLI. ET-1 and its receptors were identified in atherosclerotic popliteal arteries obtained from CLI patients undergoing lower limb amputation. In addition, plasma ET-1 levels were compared with those of non-ischaemic controls. ET-1 was associated with regions of atherosclerotic plaque, particularly in regions with high macrophage content. This peptide was also associated with endothelial cells lining the main vessel lumen as well as adventitial microvessels. ET(A) and ET(B) receptors were located within regions of plaque, adventitial microvessels and perivascular nerves. There was a statistically significant increase (P < 0.001) in plasma ET-1 in CLI patients when compared with controls. These results reveal sources of ET-1 in atherosclerotic popliteal arteries that potentially contribute to increased circulating levels of this peptide. Identification of variable receptor distributions in ischaemic tissue suggests a therapeutic potential of selective receptor targeting in patients with CLI.

Endothelin-1 and endothelin receptors in the basilar artery of the capybara

Little is known about cerebral vasculature of capybara, which seems may serve as a natural model of studying changes in cerebral circulation due to internal carotid artery atrophy at animal sexual maturation. This is the first study of the light- and electron-immunocytochemical localisation of endothelin-1 (ET-1) and ETA and ETB endothelin receptors in the basilar artery of capybaras (6 to 12-month-old females and males) using an ExtrAvidin detection method. All animals examined showed similar patterns of immunoreactivity. Immunoreactivity for ET-1 was detected in the endothelium and adventitial fibroblasts, whilst immunoreactivity for ETA and ETB receptors was present in the endothelium, vascular smooth muscle, perivascular nerves and fibroblasts. In endothelial cells immunoreactivity to ET-1 was pronounced in the cytoplasm or on the granular endoplasmic reticulum. Similar patterns of immunolabelling were observed for ETA and ETB receptors, though cytoplasmic location of clusters of immunoprecipitate seems dominant. These results suggest that the endothelin system is present throughout the wall of the basilar artery of capybara.

Nitric oxide and endothelin-1 in coronary and pulmonary circulation

Since the discovery of the vasorelaxant properties of nitric oxide and the vasoconstrictor effect of endothelin-1, there have been many studies of the distribution and functional significance of these agents in various vascular beds. In the coronary and pulmonary circulation nitric oxide and endothelin-1 actions have been largely investigated in terms of an imbalance between the opposing effects of these vasoactive agents leading to pathophysiological conditions. This article review functional and immunocytochemical studies with emphasis on the ultrastructural localization of nitric oxide synthase and endothelin-1 in the coronary and pulmonary vascular beds. Localization of nitric oxide synthase (type III or I or II) has been shown in endothelial cells, smooth muscle, and perivascular nerves of the coronary and pulmonary vascular beds and in the neurons, nerve fibers, and the small granule-containing cells within cardiac ganglia. Endothelin-1 was mainly localized in subpopulations of coronary and pulmonary endothelial cells. These immunocytochemical studies provide information about the sources of nitric oxide and endothelin-1 that contribute to the vasomotor control of cardiac and pulmonary circulation under normal and pathophysiological conditions.

Neurovascular [125I]-ET-1 binding sites on human peripheral nerve

[125I]-ET-1 binding to human peripheral nerve was studied using a combination of in vitro autoradiography and immunohistochemistry. Dense binding was predominantly to ETA receptors located on smooth muscles cells of the neural microvessels and the perineurium. These results identify regions where locally-released ET-1 may affect neural vascular perfusion and play a pathophysiological role in certain conditions, such as diabetic neuropathy.