Activity of the L-arginine/nitric oxide pathway and endothelin-1 in experimental heart failure

Neurohumoral changes influencing peripheral vascular resistance play a major role in congestive heart failure (CHF). We studied vascular function in 1-year-old cardiomyopathic syrian hamsters with pulmonary congestion and age-matched control hamsters. Aorta and mesenteric resistance arteries were suspended in organ chambers and myographs, respectively, for isometric tension recording. In aorta and mesenteric resistance arteries, contractile responses to norepinephrine (NE) were comparable in cardiomyopathic hamsters and controls. After inhibition of nitric oxide (NO) formation with nitro-L-arginine methylester (L-NAME), contractions to NE were enhanced in aorta of cardiomyopathic hamsters (p < 0.05); no effect was noted in controls or mesenteric resistance arteries. Low doses of endothelin-1 (ET-1 10(-10)-10(-9) M) caused stronger contractions in aorta of cardiomyopathic hamsters as compared with controls (p < 0.05). The sensitivity and maximal contraction to ET were more pronounced in mesenteric resistance arteries as compared with aorta in both cardiomyopathic and control hamsters (p < 0.05-0.001). In both aorta and mesenteric resistance arteries, acetylcholine (ACh 10(-9)-10(-5) M) induced concentration-dependent relaxation, which was prevented by L-NAME (p < 0.001). Maximal endothelium-dependent relaxation was more pronounced in aorta of cardiomyopathic hamsters (p < 0.05), but not different in mesenteric resistance arteries.(ABSTRACT TRUNCATED AT 250 WORDS)