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

• Published in: American journal of physiology. Lung cellular and molecular physiology 2002-07, Vol.283 (1), p.42-L51
• Main Authors: Balyakina, Elena V, Chen, Daohong, Lawrence, Mayme L, Manning, Suzanne, Parker, Richard E, Shappell, Scott B, Meyrick, Barbara
• Format: Article
• Language: English
• Subjects: Animals; Cells, Cultured; Embolism, Air - complications; Embolism, Air - physiopathology; Endothelin-1 - pharmacokinetics; Flow Cytometry; Gene Expression - physiology; Hypertension, Pulmonary - etiology; Hypertension, Pulmonary - physiopathology; Muscle, Smooth, Vascular - chemistry; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - physiopathology; Pulmonary Artery - chemistry; Pulmonary Artery - cytology; Pulmonary Artery - physiopathology; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin - analysis; Receptors, Endothelin - genetics; Receptors, Endothelin - metabolism; Sheep
• ISSN: 1040-0605; 1522-1504
• DOI: 10.1152/ajplung.00337.2001

Departments of 2  Pathology and 1  Medicine and Center for Lung Research, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2650 We examined gene and surface expression and activity of the endothelin (ET)-1 receptors (ET A and ET B ) in subendothelial (L1) and inner medial (L2) cells from the main pulmonary artery of sheep with continuous air embolization (CAE)-induced chronic pulmonary hypertension (CPH). According to quantitative real-time RT-PCR, basal gene expression of both receptors was significantly higher in L2 than L1 cells, and hypertensive L2 cells showed significantly higher gene expression of ET B than controls. Expression of both genes in hypertensive L1 cells was similar to controls. Fluorescence-activated cell sorter analysis confirmed the increased distribution of ET B in hypertensive L2 cells. Although only the ET A receptors in control L2 cells showed significant binding of [ 125 I]-labeled ET-1 at 1 h, both receptors bound ET-1 to hypertensive cells. 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 ET B (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; ET B receptor; smooth muscle cells; pulmonary hypertension; endothelin