Divergent effects of different beta-blocking agents on endothelium-dependent vasodilatation in the human forearm.
OBJECTIVE
The aim of this study was to evaluate the direct effect of three principally different beta-receptor blocking agents on endothelium-dependent vasodilatation (EDV) in the human forearm.


METHODS
In 27 young normotensive subjects forearm blood flow (FBF) was measured with venous occlusion plethysmography during local intra-arterial infusions of methacholine (MCh), evaluating EDV, and sodium nitroprusside (SNP), evaluating endothelium-independent vasodilatation (EIDV). The measurements of EDV and EIDV were undertaken at baseline conditions and repeated after 1 h of concomitant intra-arterial infusion of atenolol (n = 8, 1.2 mg/h), propranolol (n = 7, 1.2 mg/h), labetalol (n = 7, 16 mg/h) or saline (n = 5).


RESULTS
The selective beta-blocker atenolol showed a tendency to improve the FBF response to MCh (from 28.8 +/- 9.2 to 32.6 +/- 8.7 ml/min/ml tissue, p < 0.05). The nonselective beta-blocker propranolol attenuated the FBF response to MCh significantly (from 30.5 +/- 6.7 to 22.8 +/- 4.5 ml/min/ml tissue, p < 0.01). In these groups baseline FBF and EIDV were unchanged. Labetalol, a combined non-selective beta-blocker and selective alpha-1-blocker, increased baseline FBF and increased the response to both MCh and SNP in parallel (p < 0.05 for MCh and p = 0.07 for SNP). Saline did not change baseline FBF, EDV or EIDV.


CONCLUSIONS
This study showed that local infusion of different beta-blocking agents in normotensive subjects affects endothelial vasodilatory function differently. This technique could be used to evaluate the direct effect of vasoactive drugs on EDV.
von zur Můhlen
B
B
Department of Internal Medicine, University Hospital of Uppsala, Sweden. bengt.muhlen@medsci.uu.se
Millgård
J
J
Lind
L
L
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001262:Atenolol / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D004008:Diclofenac / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology*; D005260:Female; D005542:Forearm / Q000098:blood supply*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007269:Injections, Intra-Arterial; D007741:Labetalol / Q000494:pharmacology*; D008297:Male; D016210:Methacholine Chloride; D009599:Nitroprusside / Q000494:pharmacology*; D010991:Plethysmography; D011433:Propranolol / Q000494:pharmacology*; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects / Q000502:physiology; D011976:Receptors, Muscarinic / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology*
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D000894:Anti-Inflammatory Agents, Non-Steroidal; D000959:Antihypertensive Agents; D018340:Receptors, Adrenergic, alpha-1; D011976:Receptors, Muscarinic; D014665:Vasodilator Agents; D016210:Methacholine Chloride; D004008:Diclofenac; D009599:Nitroprusside; D001262:Atenolol; D011433:Propranolol; D007741:Labetalol