Jim K F, Macia R A, Matthews W D
J Pharmacol Exp Ther. 1985 Nov;235(2):377-81.
Our previous studies have shown that activation of postsynaptic alpha-2 adrenoceptors mainly utilizes extracellular calcium whereas activation of postsynaptic alpha-1 adrenoceptors mobilizes both extracellular and intracellular calcium to produce contractions in the canine saphenous vein. In the present study, the abilities of several full alpha-1 adrenoceptor agonists to release internal calcium for contractions in the canine saphenous vein were evaluated. Contractions to these alpha-1 agonists at two different equieffective concentrations (concentrations that produced 50 and 80% of the maximum phenylephrine response, PE50 and PE80, respectively) were determined in both zero external calcium medium and in normal calcium medium containing 5 mM La . If a correlation exists between the efficacy of an agonist and its ability to release internal Ca++, the contractile response to each agonist should be similar under these conditions. The results indicated marked variations in mechanical responses elicited by these alpha-1 agonists at both PE50 and PE80 concentrations. The data suggest a lack of correlation between efficacy and the ability to release internal calcium to induce contractions for a series of full alpha-1 adrenoceptor agonists in venous smooth muscle.
我们之前的研究表明，突触后α-2肾上腺素能受体的激活主要利用细胞外钙，而突触后α-1肾上腺素能受体的激活则动员细胞外和细胞内钙，以在犬隐静脉中产生收缩。在本研究中，评估了几种完全α-1肾上腺素能受体激动剂释放细胞内钙以引起犬隐静脉收缩的能力。在零细胞外钙培养基和含有5 mM镧的正常钙培养基中，测定了两种不同等效浓度（分别产生最大去氧肾上腺素反应的50%和80%的浓度，即PE50和PE80）下这些α-1激动剂引起的收缩。如果激动剂的效力与其释放细胞内Ca++的能力之间存在相关性，那么在这些条件下，对每种激动剂的收缩反应应该相似。结果表明，在PE50和PE80浓度下，这些α-1激动剂引起的机械反应存在显著差异。数据表明，对于一系列完全α-1肾上腺素能受体激动剂，在静脉平滑肌中，效力与释放细胞内钙以诱导收缩的能力之间缺乏相关性。
