Pedrinelli R, Taddei S, Graziadei L, Panarace G, Salvetti A
J Hypertens Suppl. 1986 Dec;4(5):S451-4.
Calcium channel blocking agents preferentially antagonize alpha 2-mediated pressor responses in various animal species. Whether the same happens in man is not clear. For this reason we studied the interference exerted by verapamil, a calcium entry blocker, on forearm vasoconstriction mediated by selective alpha 1- (methoxamine) and alpha 2- (B-HT 933) adrenergic agonists in untreated mild-to-moderately hypertensive patients (n = 22). Each patient underwent a single study. Forearm blood flow was recorded by strain gauge venous plethysmography; all drugs were infused into the brachial artery at systemically ineffective rates. Cumulative dose-response curves to intra-arterial methoxamine or B-HT 933 were obtained during saline or two different rates of verapamil infusion (0.9 and 3.1 micrograms/100 ml forearm tissue per min) which increased forearm blood flow dose-dependently without changing systemic blood pressure or heart rate. Either methoxamine or B-HT 933 decreased forearm blood flow during saline infusion, but their effect was blunted in a dose-dependent manner during verapamil. No evidence of preferential alpha 2-antagonism was present. At variance with animal data, calcium entry blockade by verapamil antagonizes either alpha 1- or alpha 2-mediated vasoconstriction in human forearm vessels.
钙通道阻滞剂在各种动物物种中优先拮抗α2介导的升压反应。在人类中是否也会发生同样的情况尚不清楚。因此，我们研究了钙通道阻滞剂维拉帕米对未经治疗的轻度至中度高血压患者（n = 22）中由选择性α1-（甲氧明）和α2-（B-HT 933）肾上腺素能激动剂介导的前臂血管收缩的干扰作用。每位患者均接受了单次研究。通过应变片静脉体积描记法记录前臂血流量；所有药物均以全身无效的速率注入肱动脉。在生理盐水或两种不同速率的维拉帕米输注（0.9和3.1微克/100毫升前臂组织每分钟）期间，获得了对动脉内甲氧明或B-HT 933的累积剂量-反应曲线，这两种速率均使前臂血流量呈剂量依赖性增加，而不改变全身血压或心率。在生理盐水输注期间，甲氧明或B-HT 933均可降低前臂血流量，但在维拉帕米输注期间，它们的作用以剂量依赖性方式减弱。未发现优先拮抗α2的证据。与动物数据不同，维拉帕米的钙通道阻滞作用可拮抗人类前臂血管中α1或α2介导的血管收缩。
