Role of endogenous endothelin-1 in experimental renal hypertension in dogs.
BACKGROUND
Endothelin-1, a vasoconstrictive peptide released by endothelium, may be involved in the pathophysiology of hypertension. The goal of the present study was to evaluate the role of endogenous endothelin-1 in renal hypertension in dogs. The model of hypertension consisted of silk tissue wrapping of the left kidney, which produced hypertension associated with perinephritis after 6 to 8 weeks.


RESULTS
Thirty-two anesthetized open chest dogs were studied randomly: 8 dogs with perinephritic hypertension received the nonpeptidic ETA-ETB receptor antagonist bosentan (group 1); 8 other hypertensive dogs received the vehicle solution (group 2); 8 healthy dogs received bosentan (group 3); and 8 healthy dogs received the vehicle solution (group 4). Bosentan was injected as an intravenous bolus (3 mg/kg) followed by a 1-hour infusion at a rate of 7 mg.kg-1.h-1. In hypertensive dogs, bosentan produced a similar decrease (P = .0001) of both left ventricular systolic and mean aortic pressures, which averaged 38 mm Hg (-22% and -24%, respectively). These parameters remained unchanged with the vehicle solution. Left ventricular end-diastolic and left atrial pressures also declined significantly with bosentan (P = .0005 and P < .05, respectively). Left ventricular lengths tended to decrease. The other cardiovascular parameters (heart rate, peak [+]dP/dt, time constant of relaxation, and coronary vascular resistance) did not change significantly. In healthy dogs, bosentan decreased mean aortic pressure by 19 mm Hg (P = .004). Vehicle solution had no effect. Plasma endothelin-1 levels, similar under basal conditions in healthy and hypertensive dogs, increased 30-fold with bosentan (P = .0001).


CONCLUSIONS
Specific endothelin-1 receptor antagonism markedly lowers blood pressure in experimental hypertension but is less effective on blood pressure of healthy animals. This suggests that endothelin-1 plays a role in the pathophysiology of hypertension but contributes to a lesser extent to the maintenance of normal blood pressure. This role of endothelin-1 is unrelated to its plasma levels. The increase of plasma endothelin-1 with bosentan, due either to a displacement of endothelin-1 from its receptor or to a feedback mechanism, does not prevent this blood pressure reduction.
Donckier
J
J
Division of Endocrinology, University Hospital UCL of Mont-Godinne, Yvoir, Belgium.
Stoleru
L
L
Hayashida
W
W
Van Mechelen
H
H
Selvais
P
P
Galanti
L
L
Clozel
J P
JP
Ketelslegers
J M
JM
Pouleur
H
H
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D000077300:Bosentan; D004285:Dogs; D016232:Endothelins / Q000097:blood / Q000502:physiology*; D004837:Epinephrine / Q000097:blood; D006339:Heart Rate / Q000187:drug effects; D006977:Hypertension, Renal / Q000209:etiology*; D009638:Norepinephrine / Q000097:blood; D013449:Sulfonamides / Q000494:pharmacology*
D016232:Endothelins; D013449:Sulfonamides; D000077300:Bosentan; D009638:Norepinephrine; D004837:Epinephrine