[Effect of alpha-adrenergic receptor blockade on peripheral vasoconstriction induced by the cold pressor test. Evidence for functional integrity of alpha 1 and alpha 2 adrenergic receptors in patients with congestive heart failure].

Central sympathetic stimulation results in direct vascular vasoconstriction mediated by activation of alpha-adrenergic receptors. However, it is unknown whether this vasoconstriction is mediated by alpha 1 or alpha 2-adrenoceptor subtypes. In patients with congestive heart failure (CHF), both circulating and neuronally released catecholamines produces vasoconstriction via alpha-adrenergic stimulation. This vasoconstriction produces detrimental hemodynamic effect in CHF patients since it increases right and left ventricular filling pressures and pulmonary and systemic vascular resistances. While the myocardial alpha 1-adrenoceptors seems not to be down-regulated in heart failure, the functional integrity of vascular alpha 1 and alpha 2-adrenoceptors in CHF remains to be elucidated. Accordingly, the present study was designed to assess whether the limb vascular response to alpha 1 or alpha 2-adrenoceptor stimulation is impaired in patients with CHF. We studied 25 control subjects and 19 patients with CHF due to primary dilated cardiomyopathy. Forearm blood flow was measured by venous occlusion plethysmography. Sympathetic stimulation was produced by cold. The intraarterial pump-infusions of BHT 933 (a selective alpha 2-adrenoceptors agonist agent, 0.1, 1, 10 micrograms/kg/min for 5 min) produced the same peripheral vasoconstriction in CHF and in control subjects: 32 +/- 23.9%, 47.3 +/- 20% and 55 +/- 26.1% respectively at I, II, and III dose in CHF and 28.7 +/- 38.6%, 36 +/- 14.5%, and 57 +/- 13.8% respectively at I, II, and III dose in control subjects. The dose response to BHT 933 was not different in the 2 groups.(ABSTRACT TRUNCATED AT 250 WORDS)