Endothelium-dependent and -independent vasoreactivity of rat basilar artery in chronic heart failure

Alterations of vasoreactivity are a well-known phenomenon in chronic heart failure (CHF), and activation of the endogenous endothelin (ET) system is suspected to contribute significantly. Regional differences in alterations of vasoreactivity exist; however, nothing is known about cerebrovascular reactivity in CHF. This is of interest in view of increased stroke risk in CHF. Therefore, 12 weeks after coronary artery ligation to induce CHF in rats, studies of vasoreactivity of the isolated basilar artery (BA) were performed and compared with third-order branches (MA-A3) and the main trunk (MA) of the superior mesenteric artery. Some of the animals received longterm ET-receptor antagonism by 11 weeks of treatment with the selective ETA-receptor antagonist LU 135252 or the mixed ETA/ETB-receptor antagonist bosentan. In rats with CHF, endothelium-dependent relaxation by acetylcholine and A23187 as well as endothelium-independent relaxation by sodium nitroprusside (SNP) was largely unaffected in BA or MA. However, in MA-A3, potency of SNP was diminished without change of maximal effect. ET-1-induced contraction did not differ in arteries from CHF and control rats, either in placebo- or ET-receptor antagonist-treated animals. In summary, there was essentially no change of vascular reactivity in similar sized arteries obtained from brain and mesentery. This is in contrast to results on arteries from a variety of vascular regions published previously, thus supporting the concept of organ- and probably time-related changes of vascular function in the development of CHF. The absence of significant alteration of cerebral vasoreactivity may be taken to indicate that changes in cerebral blood flow and increased incidence of ischemic stroke in patients with CHF are caused not by local alterations of vascular function.