Effects of beta-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 microgram/ml in the perfusate dl-propranolol and pindolol significantly increased vascular resistance by blockade of beta2-receptor mediated vasodilatation, whereas atenolol, bunitrolol and methypranol had no effect on peripheral resistance at this concentration. With increasing concentrations up to 10 microgram/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 beta2-receptors at low concentrations of atenolol and also bunitrolol and methypranol show relative selectivity for beta1-receptors. The differential effects of beta-adrenergic agents on vascular resistance may have significance for the clinical use of the drugs.