ET-1 receptor gene expression and distribution in L1 and L2 cells from hypertensive sheep pulmonary artery

Abstract

Exposure to exogenous ET-1 for 18 h revealed that only the L2 cells internalized ET-1, and internalization by hypertensive L2 cells was significantly reduced when compared with controls. Treatment with ET A (BQ-610) and ETB (BQ-788) receptor antagonists demonstrated that both receptors contributed to internalization of ET-1 in control L2 cells, whereas in hypertensive cells only when both receptor antagonists were used in combination was significant suppression of ET-1 internalization found. We conclude that in sheep receiving CAE, alterations in ET B receptors in cells of the L2 layer may contribute to the maintenance of CPH via alterations in their expression, distribution, and activity.ET A receptor; ETB receptor; smooth muscle cells; pulmonary hypertension; endothelin SINCE ITS DISCOVERY 12 YEARS AGO, endothelin (ET) has been shown to contribute to a wide variety of physiological and pathophysiological processes in various systems (22). The ET family of 21 amino acid peptides exists in three distinct isoforms: ET-1, ET-2, and ET-3. It is an extremely potent vasoconstrictor resulting in slowly developing and sustained contraction. Although the endothelial cell was originally described as the source of ET-1, it is now known that several other cell types, including pulmonary vascular smooth muscle cells, synthesize this peptide (33, 36).The biological effects of ET-1 are mediated by two distinct ET receptor subtypes, ET A and ET B (1, 35). The affinity of the ET A receptor for ET-1 has been shown to be ϳ100 times that for ET-3 (ET-1 Ͼ ET-2 Ͼ ET-3), whereas the affinity of the ET B receptor is equipotent for all three isoforms of ET (34). Early reports indicated that the ET A receptor on smooth muscle was responsible for the vasoconstrictor effect of ET-1, whereas the ET B receptor on endothelial cells modulated ET-1-induced vasodilation. However, recent pharmacological studies suggest that there are two classes of ET B with cell specific effects, ET B1 on endothelial cells mediating vasodilation and ET B2 on smooth muscle cells mediating vasoconstriction (9). The ET B receptor also functions as a "clearance receptor" and is particularly important in the lung, where 50% of ET-1 is retained (22,29).ET-1 has been linked to the development of chronic pulmonary hypertension (CPH). Increased expression of the peptide has been demonstrated in endothelial cells of pulmonary arteries from patients with idiopathic and secondary forms of pulmonary hypertension (15), and arterial-to-venous ratios of ET-1 protein were found to be elevated above the normal range in patients with pulmonary hypertension (40). Several studies have linked increased expression of ET-1 to the development of hypoxia-induced CPH in rats (5, 24), and use of ET-1 receptor antagonists has been shown both to inhibit progression of the disease and to promote recovery (4,10,43).Although these studies support a central role for ET-1 in the pathogenesis of CPH, the picture is likely more complicated than first suspected, in that prepro-ET-1 (ppET-1) mRNA is...

Hypoxic Pulmonary Arterial Hypertension in the Chicken Model

“…Contrary to previous reports in the lungs of hypoxic rats (Li et al, 1994) and in cells from the pulmonary artery of PH sheep (Balyakina et al, 2002), our work showed a decrease in ETA mRNA levels in the lungs of PHB ( Figure 5). Thus, HPB showed high values of mRNA ET-1 and lowest values of mRNA of eNOS, and NHPB had opposite results (data non published).…”

“…The distribution and density of ET-1 receptors on vascular SMC varies among species and their location in the corresponding blood vessel (Nishimura et al, 1995;Chen and Oparil, 2000;Balyakina et al, 2002). Nevertheless, the role of ET-1 receptors that mediate the vasoconstrictor response in this animal model requires further study.…”

Cyclooxygenase is regulated by ET-1 and MAPKs in peripheral lung microvascular smooth muscle cells

“…The present study demonstrates that both vasoconstrictor and vasodilator agents are synthesized by PLVSMC. In previous studies, we demonstrated that ET-1 is synthesized in smooth muscle cells isolated from control sheep main and midregion pulmonary artery and suggested that these cells may contribute to local arterial tone (3,4). We also demonstrated that ppET-1 gene expression was regulated by exogenous ET-1, as has also been shown in rat endothelial and vascular smooth muscle cells (18,25).…”

“…Measurement of intracellular ET-1. Intracellular levels of mature ET-1 were determined in homogenates of PLVSMC as previously described (3,39). Briefly, the cells were washed in serum-free medium, trypsinized, and centrifuged at 1,000 rpm for 10 min.…”

Expresión de Endotelina-1 en pollos con hipertensión arterial pulmonar por hipoxia hipobárica

“…Así, la serotonina (20), los receptores ETA y ETB de la ET-1 (9,19,21), la sintasa de óxido nítrico (22)(23)(24), el factor de crecimiento del tejido conectivo y la adrenomedulina (19). Dado que las moléculas estudiadas son factores clave en la patogénesis ya sea como vasoconstrictores o vasodilatadores de los vasos pulmonares, ellos deben actuar en armonía en condiciones fisiológicas y cualquier A, pulmonary hypertensive birds (subjected to hypoxia), B, non-pulmonary hypertensive birds subjected to hypoxia, and C, non-pulmonary hypertensive birds not subjected to hypoxia.…”