The cardiac endothelin system in established pressure overload left ventricular hypertrophy.
In normal hearts, endothelin-1 (ET-1) has been shown to initiate myocyte growth and to modulate cardiac function. However, regulation of the various components of the system and the functional effects of ET-1 in established left ventricular hypertrophy (LVH) are less clear. We thus studied ET-1, ET(A) receptor, and endothelin converting enzyme (ECE-1) mRNA regulation as well as the effects of ET-1 on coronary resistance, LV contractility and relaxation in hypertrophied rat hearts. Cardiac pressure overload, secondary to banding of the ascending aorta, resulted in a transient increase of cardiac ET-1 and ET(A) receptor mRNAs that reached a maximum at 2 days (+75% and +40%, respectively, P<0.05, each). ET-1 mRNA levels reached a second peak at 84 days of pressure overload (+60%, P<0.05), at the later time point in conjunction with elevated ECE-1 mRNA levels (+20%, P<0.05). The functional implications of ET-1 were examined in a study of isolated perfused hearts. Both hearts with established LVH and sham control hearts responded to ET-1 perfusion (10(-1)] to 10(-9) M) with an increase of coronary perfusion pressure (CPP; +85+/-15 and +75+/-8 mm Hg; P<0.001 each) and a slight decrease of LV systolic pressure (LVP; -12+/-9 and -9+/-7 mm Hg; P = NS). In contrast, ET-1 increased LV end-diastolic pressure (LVEDP) only in LVH hearts (+22+/-7 mm Hg, P<0.05 versus baseline and +20+/-7 mm Hg, P<0.05 versus sham). Direct stimulation of protein kinase C mimicked the effects of ET-1, whereas inhibition of this kinase or the Na+ -H+ exchanger blunted the effects of ET-1 on CPP, LVP, and LVEDP. Interestingly, coadministration of the vasodilator and the nitric oxide (NO) donor nitroglycerin not only prevented the increase of CPP and LVEDP, but also uncovered a slight positive inotropic effect of ET-1 in LVH hearts. Thus, the cardiac expression of ET-1, ET(A), and ECE-1 mRNAs displays a distinct pattern during early and advanced cardiac pressure overload. Furthermore, ET-1 mediates a slight depression of systolic, and a profound depression of diastolic, functional parameters in hearts with established LVH, effects that appear to be secondary to ET-1-related coronary vasoconstriction. The data suggest a functional role of the endothelin system in hearts with established pressure overload hypertrophy.
Schunkert
H
H
Klinik und Poliklinik für Innere Medizin II, University of Regensburg. Germanyheribert.schunkert@klinik.uni-regensburg.de
Orzechowski
H D
HD
Böcker
W
W
Meier
R
R
Riegger
G A
GA
Paul
M
M
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001018:Aortic Diseases / Q000150:complications; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D001794:Blood Pressure / Q000502:physiology; D019332:Endothelin-1 / Q000378:metabolism*; D000072396:Endothelin-Converting Enzymes; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017379:Hypertrophy, Left Ventricular / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D066298:In Vitro Techniques; D008297:Male; D008666:Metalloendopeptidases; D009206:Myocardium / Q000378:metabolism; D005996:Nitroglycerin / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology
D019332:Endothelin-1; D004791:Enzyme Inhibitors; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin; D000584:Amiloride; D011493:Protein Kinase C; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; D000072396:Endothelin-Converting Enzymes; D005996:Nitroglycerin; D019311:Staurosporine