title: Exaggerated coronary reactivity to endothelin-1 in diabetes: reversal with bosentan.
abstract: We previously demonstrated that chronic endothelin receptor blockade (with bosentan) improved functional cardiac performance in streptozotocin-diabetic rats, suggesting a novel role of endothelin-1 (ET-1) in modulating diabetic heart dysfunction. To gain insight into the mechanism(s) underlying this effect, we examined the coronary vascular responses to ET-1 in hearts from diabetic and control rats treated with or without bosentan. Rats were divided into control, control-treated, diabetic, and diabetic-treated groups. The control-treated and diabetic-treated groups received bosentan (100 mg x kg(-1) x d(-1)) for 8 weeks. Following treatment, hearts were isolated and perfused, and coronary reactivity to ET-1 was assessed by measuring the changes in coronary perfusion pressure in response to ET-1 (50 and 100 pM). Additionally, maximal coronary blood flow (assessed with 10(-5) M adenosine) was measured in isolated perfused hearts. The key observation is that coronary reactivity to ET-1 was significantly higher in the diabetic than the control rats. This effect was normalized in diabetic rats chronically receiving bosentan. Maximal coronary vasodilation did not differ between the four groups. In conclusion, the reactivity of ET-1 is altered in the isolated perfused coronary vascular bed from diabetic rats, and chronic ET receptor blockade restores this reactivity to control values. These observations provide a possible mechanism for the improvement in diabetic heart function observed after chronic bosentan treatment.
authors.affiliation: Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, The University of British Columbia, 2146 East Mall, Vancouver, BC V6T 1Z3, Canada.
authors.forename: Subodh
authors.initials: S
authors.lastname: Verma
authors.forename: Emi
authors.initials: E
authors.lastname: Arikawa
authors.forename: Sammy
authors.initials: S
authors.lastname: Lee
authors.forename: Aaron S
authors.initials: AS
authors.lastname: Dumont
authors.forename: Linfu
authors.initials: L
authors.lastname: Yao
authors.forename: John H
authors.initials: JH
authors.lastname: McNeill
mesh_terms: D000818:Animals; D000077300:Bosentan; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000503:physiopathology*; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology* / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013449:Sulfonamides / Q000494:pharmacology*; D013997:Time Factors; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
chemical_list: D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D013449:Sulfonamides; D014662:Vasoconstrictor Agents; D000077300:Bosentan