The role of endothelin-1 in regulation of rat mesenteric microcirculation

Ultrastructural Analysis of Secretory Granules of Myocardial Capillary Endothelium in Cardiosurgical Stress

In patients with chronic myocardial tissue hypoxia irrespective of the disease (Fallot's tetralogy, coronary disease) factors of cardiosurgical stress initiate a drop of secretory production in coronary capillary endothelium and obstruction of the intravascular space by blood cells. In children the peak of exocytosis of secretory granules coincides with the period of aortic occlusion, while in adults it is attained at the stage of reperfusion.

Remodeling of resistance arteries in renal failure: effect of endothelin receptor blockade

Remodeling of vessels is a known feature of renal failure, but it is unclear whether this represents an appropriate or inappropriate response to the known changes in blood flow, shear stress, and wall tension. To investigate remodeling in response to variations in blood flow, first-order mesenteric arteries were exposed to high- and low-flow conditions via the ligation of second-order branches, according to the technique described by Pourageaud and De Mey. The resulting changes in vessel geometric features, relative proportions of intima and media, submicroscopic structure, and immunostaining for proliferating cell nuclear antigen (PCNA), endothelin-1 (ET-1), and ET(A) receptors were assessed in first-order mesenteric arteries under low-flow and high-flow conditions. Subtotally nephrectomized (SNX) animals were compared with sham-operated rats. Animals either were left untreated or were treated with the ET(A) receptor antagonist (ET-RA) LU-135252, because of suggestions in the literature that ET is involved in vascular remodeling in uremia. A highly significant increase in intimal thickness was noted in low-flow arteries (4.21 +/- 1.39 microm) of SNX animals, compared with normal-flow arteries (2.06 +/- 0.61 microm), but this increase was not observed in sham-operated rats (1.38 +/- 0.77 in low-flow arteries versus 2.40 +/- 0.35 microm in normal-flow arteries). The increase in intimal thickness in low-flow arteries was abrogated by ET-RA. The medial thickness was increased in untreated SNX animals (19.5 +/- 3.61 microm), compared with sham-operated rats, and this increase was also prevented by ET-RA. The medial thickness was not affected by low flow in either sham-operated or SNX animals. In parallel, the number of PCNA-positive intimal cells was higher in low-flow, but not high-flow, arteries of SNX rats, compared with sham-operated rats. No significant change was observed in sham-operated animals. In the media, the number of PCNA-positive cells was higher in untreated SNX animals than in sham-operated rats. The number was even more markedly increased in high-flow, but not low-flow, vessels. This increase was abrogated by ET-RA. It is concluded that, in uremic animals, the response of the intima to low flow and the response of the media to high flow are exaggerated. Both responses are apparently mediated by ET.

Endothelial dysfunction in cirrhosis and portal hypertension

Portal hypertension (PHT) is a common clinical syndrome associated with chronic liver diseases; it is characterized by a pathological increase in portal pressure. Pharmacotherapy for PHT is aimed at reducing both intrahepatic vascular tone and elevated splanchnic blood flow. Due to the altered hemodynamic profile in PHT, dramatic changes in mechanical forces, both pressure and flow, may play a pivotal role in controlling endothelial and vascular smooth muscle cell signaling, structure, and function in cirrhotics. Nitric oxide, prostacyclin, endothelial-derived contracting factors, and endothelial-derived hyperpolarizing factor are powerful vasoactive substances released from the endothelium in response to both humoral and mechanical stimuli that can profoundly affect both the function and structure of the underlying vascular smooth muscle. This review will examine the contributory role of hormonal- and mechanical force-induced changes in endothelial function and signaling and the consequence of these changes on the structural and functional response of the underlying vascular smooth muscle. It will focus on the pivotal role of hormonal and mechanical force-induced endothelial release of vasoactive substances in dictating the reactivity of the underlying vascular smooth muscle, i.e., whether hyporeactive or hyperreactive, and will examine the extent to which these substances may exert a protective and/or detrimental influence on the structure of the underlying vascular smooth muscle in both a normal hemodynamic environment and following hemodynamic perturbations typical of PHT and cirrhosis. Finally, it will discuss the intracellular processes that regulate the release/expression of these vasoactive substances and that control the transformation of this normally protective cell to one that may promote the development of vasculopathy in PHT.

Differentiated effects on splanchnic homeostasis by selective and non-selective endothelin receptor antagonism in porcine endotoxaemia

1. The non-selective endothelin (ET) receptor antagonist bosentan has been shown to restore systemic and gut oxygen delivery and reverse intestinal mucosal acidosis in porcine endotoxin shock. 2. To further elucidate the specific role of the ETA as opposed to the ETB receptor and their effects in the splanchnic region a non-selective (ET(MIX)ra) A-182086 and selective ETA (ET(A)ra) PD155080 and ETB (ET(B)ra) A-192621 receptor antagonists were administered, separately or simultaneously (ET(A+B)ra) 2 h after onset of endotoxin shock. These four groups were compared to a control group receiving only endotoxin and vehicle. 3. Thirty-nine pigs were anaesthetized and catheterized for measurement of central and regional haemodynamics. A tonometer in the distal ileum was used for measurement of mucosal PCO2. Blood gases and plasma ET-1-LI levels as well as histological samples from the gut were assessed. Intervention was started 2 h after onset of endotoxemia and the experiments were terminated after 5 h. 4. Endotoxin-induced changes in systemic, gut oxygen delivery and portal hepatic vascular resistance and systemic acidosis were effectively counteracted by both ET(A+B)ra an ET(MIX)ra. ET(A)ra administration was not effective while ET(B)ra proved to be fatal as all animals in this group died prior to full time of the experiment. While both ET(A+B)ra and ET(MIX)ra improved gut oxygen delivery only the latter attenuated the profound endotoxin-induced ileal mucosal acidosis. 5. The lethal effect seen from selective ETB receptor antagonism in the current study may be due to increased ETA receptor activity as plasma levels of ET-1 is increased several fold by blocking the ETB receptor and thereby the plasma-ET-1-clearing function. Furthermore, a loss of endothelial ETB receptor vasodilating properties may also have contributed to the lethal course in the ET(B)ra group. 6. The findings in this study suggest that ET is involved in the profound endotoxin-induced disturbances in splanchnic homeostasis in porcine endotoxaemia. Furthermore, antagonism of both ETA and ETB receptors is necessary to effectively counteract these changes.