Increased endothelin-1 binding sites in the cardiac membranes in rats with chronic heart failure.
The effects of experimental chronic heart failure (CHF) on the density and affinity for endothelin-1 (ET-1) binding was studied in the rat heart. Because it has been reported that ET-1 binding sites on cultured cardiocytes are downregulated by pretreatment with ET-1, we also studied the plasma concentrations of ET-1 in rats with CHF. Three weeks after ligation of the left coronary artery, rats developed chronic heart failure (CHF rats). The plasma concentrations of ET-1, as measured by a sandwich-enzyme immunoassay, were significantly higher in CHF rats than in sham-operated rats [4.80 +/- 0.33 vs. 0.91 +/- 0.11 (mean +/- SEM) pg/ml; p < 0.01]. [125I]ET-1 binding experiments on rat cardiac membranes revealed that the binding site density (Bmax) was significantly higher in the CHF rats than in the sham-operated rats (243.0 +/- 20.0 vs. 154.8 +/- 17.4 fmol/mg protein; p < 0.05), whereas the values for the dissociation constant (Kd) were not different between the two groups (28.7 +/- 7.0 vs. 29.8 +/- 1.9 pM). Therefore, in the CHF rats, although plasma concentrations of ET-1 were elevated, the density of myocardial ET receptors was increased. Because ET-1 has potent inotropic and hypertrophic effects on cardiac myocytes, it is suggested that the effects of endogenous ET-1 in the heart are different between the CHF rats and the sham-operated rats.
Miyauchi
T
T
Department of Internal Medicine, Institute of Clinical Medicine and Department of Pharmacology, University of Tsukuba, Japan.
Sakai
S
S
Ihara
M
M
Kasuya
Y
Y
Yamaguchi
I
I
Goto
K
K
Sugishita
Y
Y
D000818:Animals; D001665:Binding Sites; D002908:Chronic Disease; D016232:Endothelins / Q000378:metabolism; D006333:Heart Failure / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017466:Receptors, Endothelin / Q000032:analysis*
D016232:Endothelins; D017466:Receptors, Endothelin