Diabetic state, high plasma insulin and angiotensin II combine to augment endothelin‐1‐induced vasoconstriction via ETA receptors and ERK

• Published in: British journal of pharmacology Vol. 155; no. 7; pp. 974 - 983
• Main Authors: Kobayashi, T, Nogami, T, Taguchi, K, Matsumoto, T, Kamata, K
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.12.2008; Nature Publishing Group
• Subjects: angiotensin; Angiotensin II - metabolism; Angiotensin II - pharmacology; Angiotensin II Type 1 Receptor Blockers - pharmacology; Animals; Aorta - metabolism; Aorta - physiopathology; Biological and medical sciences; contraction; diabetes; Diabetes Mellitus, Experimental - complications; Diabetes Mellitus, Experimental - physiopathology; Diabetes Mellitus, Type 1 - complications; Diabetes Mellitus, Type 1 - physiopathology; Diabetes. Impaired glucose tolerance; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; endothelin; Endothelin A Receptor Antagonists; Endothelin-1 - metabolism; Etiopathogenesis. Screening. Investigations. Target tissue resistance; Extracellular Signal-Regulated MAP Kinases - metabolism; Gene Expression Regulation - drug effects; hyperinsulinaemia; Hypertension - etiology; Insulin - blood; Insulin - metabolism; Insulin - pharmacology; Losartan - pharmacology; Male; Medical sciences; Mitogen-Activated Protein Kinases - metabolism; Pharmacology. Drug treatments; Rats; Rats, Wistar; Receptor, Endothelin A - metabolism; Research Papers; Streptozocin; Vasoconstriction - drug effects; Endocrinopathy; Hyperinsulinemia; Biological fluid; Pancreatic hormone; Extracellular signal-regulated protein kinase; Enzyme; Transferases; Diabetes mellitus; Peptide hormone; Vasoconstriction; Mitogen-activated protein kinase; Endothelin 1; Insulin; ETA endothelin receptor; Blood plasma; endothelin; Octapeptide; Renin angiotensin system; Vasomotricity; angiotensin; contraction; hyperinsulinaemia; Angiotensin II; diabetes
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/bjp.2008.327

Background and purpose: Mechanisms associated with the enhanced contractile response to endothelin‐1 in hyperinsulinaemic diabetes have been examined using the rat aorta. Functions for angiotensin II, endothelin‐1 receptor expression and extracellular signal‐regulated kinase (ERK) have been investigated. Experimental approach: Streptozotocin‐induced diabetic rats were infused with angiotensin II or, following insulin treatment, were treated with losartan, an angiotensin II receptor antagonist. Contractions of aortic strips with or without endothelium, in response to endothelin‐1 and angiotensin II, were examined in vitro. Aortic ETA receptors and ERK/MEK expression were measured by western blotting. Key results: Insulin‐treated diabetic rats exhibited increases in plasma insulin, angiotensin II and endothelin‐1. The systolic blood pressure and endothelin‐1‐induced contractile responses in aortae in vitro were enhanced in insulin‐treated diabetic rats and blunted by chronic losartan administration. LY294002 (phosphatidylinositol 3‐kinase inhibitor) and/or PD98059 (MEK inhibitor) diminished the enhanced contractile response to endothelin‐1 in aortae from insulin‐treated diabetic rats. ETA and ETB receptors, ERK‐1/2 and MEK‐1/2 protein expression and endothelin‐1‐stimulated ERK phosphorylation were all increased in aortae from insulin‐treated diabetic rats. Such increases were blunted by chronic losartan administration. Endothelin‐1‐induced contraction was significantly higher in aortae from angiotensin II‐infused diabetic rats. angiotensin II‐infusion increased ERK phosphorylation, but the expression of endothelin receptors and ERK/MEK proteins remained unchanged. Conclusions and implications: These results suggest that the combination of high plasma angiotensin II and insulin with a diabetic state induced enhancement of endothelin‐1‐induced vasoconstriction, ETA receptor expression and ERK expression/activity in the aorta. Losartan improved both the diabetes‐related abnormalites and the diabetic hypertension. British Journal of Pharmacology (2008) 155, 974–983; doi:10.1038/bjp.2008.327; published online 18 August 2008