Comparative effects of some calcium-channel blockers on human peripheral arteries and veins

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Abstract
Comparative effects of some calcium‐channel blockers on human peripheral arteries and veins. Acta Physiol Scand 130, 419–427. Received 5 December 1986, accepted 9 February 1987. ISSN 0001–6772. Departments of Surgery and Clinical Pharmacology, Lund University, Sweden. We investigated the effects of five different calcium‐channel blockers (CCBs), verapamil, nifedipine, diltiazem, flunarizine and lidoflazine, on contractions evoked an vitro by noradrenaline (NA) in small human arteries and veins from the epigastric region. Vessels were obtained from patients without obvious vascular diseases undergoing surgery because of inguinal hernias. The human superficial epigastric artery has previously been shown to contain mainly α1‐adrenoceptors, whereas in the vein α2‐adrenoceptors predominate. In experiments where NA (10‐5 m) was added non‐cumulatively, it was found that nifedipine was the most potent relaxant agent in both arteries and veins, but that this drug showed no preference for any type of vessel. In contrast verapamil (10‐6 m) and (10‐5 m) diltiazem, flunarizine and lidoflazine inhibited the NA‐induced contractions to a significantly greater extent in the arteries than in the veins. Comparison between diltiazem and nifedipine on contractions induced by cumulative addition to NA showed that both drugs had significantly more depressive effects on arteries than on veins if the vessels were contracted by relatively high concentrations of NA (10‐‐6 and 10‐‐5 m). The results thus confirm the clinical finding that CCBs have more pronounced effects on the arterial than on the venous side of the circulation. They do not support the view that CCBs are more effective inhibitors of α2‐‐ than α1‐adrenoceptor mediated contraction in isolated human blood vessels.