Chronic endothelin antagonism restores cerebrovascular function in diabetes.
OBJECTIVE
Diabetes profoundly alters vascular function and is a risk factor for cerebrovascular disease. Diabetes increases myogenic tone and decreases responsiveness to adenosine triphosphatase (ATP)-sensitive K(+) (K(ATP)) channel openers and endothelium-dependent vasodilators. The mechanism(s) by which diabetes impairs cerebrovascular function remain obscure. In the present study, the effects of the potent vasoactive peptide endothelin-1 on myogenic tone and endothelium-dependent and potassium channel-mediated vasodilation in middle cerebral arteries from diabetic and nondiabetic rats were investigated.


METHODS
Twenty-eight Wistar rats were divided into four experimental groups (n = 7 per group): control (C), control treated with bosentan (an endothelin A/B receptor antagonist) (CB), diabetic (D), and diabetic bosentan-treated (DB). Diabetes was induced with streptozotocin (D and DB groups), after which chronic bosentan treatment was initiated (CB and DB groups). Middle cerebral arteries were mounted in a pressure myograph, and myogenic responses were recorded. In addition, endothelium-dependent and -independent responses and the effects of the K(ATP) channel opener pinacidil were examined.


RESULTS
Cerebral arteries from the diabetic and nondiabetic rats constricted in response to graded pressure increases. Maximum myogenic responses (percent constriction at 60 mm Hg) were significantly greater in the D group (38 +/- 3% versus 25 +/- 3% in C; P < 0.02). The enhanced myogenic tone in the D group was completely prevented by bosentan treatment (DB, 23 +/- 5% versus D; P < 0.003) without an effect on the CB group. In addition, bosentan treatment improved endothelium-dependent vasomotion and improved K(ATP)-mediated vasodilation in the DB group (P < 0.001).


CONCLUSIONS
These data describe, for the first time, the interaction between endothelin-1, myogenic tone, and endothelial function in diabetes. Chronic endothelin antagonism restores cerebrovascular function in this model of diabetes and has global implications for the management of cerebrovascular disease in diabetes.
Dumont
Aaron S
AS
Department of Neurological Surgery, University of Virginia, Charlottesville, Virginia 22908, USA. asd2f@virginia.edu
Dumont
Randall J
RJ
McNeill
John H
JH
Kassell
Neal F
NF
Sutherland
Garnette R
GR
Verma
Subodh
S
D000818:Animals; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D000077300:Bosentan; D002561:Cerebrovascular Disorders / Q000188:drug therapy* / Q000209:etiology* / Q000503:physiopathology; D048909:Diabetes Complications; D003920:Diabetes Mellitus / Q000503:physiopathology*; D004195:Disease Models, Animal; D065128:Endothelin Receptor Antagonists; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology; D008297:Male; D020768:Middle Cerebral Artery / Q000187:drug effects* / Q000503:physiopathology*; D024510:Muscle Development / Q000187:drug effects / Q000502:physiology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D017466:Receptors, Endothelin / Q000627:therapeutic use*; D020127:Recovery of Function / Q000187:drug effects* / Q000502:physiology*; D013449:Sulfonamides / Q000627:therapeutic use*; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology*
D000959:Antihypertensive Agents; D065128:Endothelin Receptor Antagonists; D015221:Potassium Channels; D017466:Receptors, Endothelin; D013449:Sulfonamides; D000077300:Bosentan