Effects of β-adrenergic blocking agents on peripheral vascular resistance

The effects of the beta-adrenergic blocking agents propranolol, pindolol, atenolol, bunitrolol, and methypranol on the vascular resistance of isolated perfused hindlimbs of rats were investigated. At concentrations of 0.01 μg/ml in the perfusate dl-propranolol und pindolol significantly increased vascular resistance by blockade of β₂-receptor mediated vasodilatation, whereas atenolol, bunitrolol and methypranol had no effect on peripheral resistance at this concentration. With increasing concentrations up to 10 μg/ml all drugs, with the exception of atenolol, caused vasodilatation. We conclude that the specificity of beta-blocking agents can be established in the isolated perfused hindlimb vasculature of rats through its effect on vascular resistance. The lack of inhibition of vascular β₂-receptors at low concentrations of atenolol and also bunitrolol and methypranol show relative selectivity for β₁-receptors. The differential effects of β-adrenergic agents on vascular resistance may have significance for the clinical use of the drugs.