Alterations in vascular reactivity in isolated vessel segments from dogs with naturally occurring heart failure

To investigate if functional vascular reactivity is altered in heart failur e, the reactivity of isolated canine saphenous vein (sv) and femoral artery (FA) rings, from control dogs and dogs with naturally occurring heart fail ure was examined. In both vessels, relaxation responses to the endothelium- dependent vasodilator, acetylcholine were unaffected by heart failure. In t he FA, in heart failure, there was a significant reduction in the potency o f the agonist noradrenaline (pEC(50) 6.05+/-007 (N = 8) and 5.54 +/- 0.13 ( N = 7) for control and heart failure respectively). There was no significan t alteration in potency in the sv. In addition, in the FA the maximum respo nses to both noradrenaline (control 3.64 +/- 0.31 KPa, (N = 8); failure 5.1 1 +/- 0.35 KPa, (N = 7) P = 0.004) and potassium chloride (control 2.18 +/- 0.26 KPa, (N = 8); failure 4.46 +/- 0.25 KPa, (N = 7) P = 0.001) were sign ificantly increased in heart failure. It is suggested that enhanced agonist induced responses, in the femoral artery, in dogs with heart failure, may limit blood flow to exercising skeletal muscle and subsequently reduce exer cise tolerance. (C) 1999 Harcourt Publishers Limited.