Paspaliaris V, Leaver D D
Department of Pharmacology, University of Melbourne, Parkville, Victoria, Australia.
J Bone Miner Res. 1991 Aug;6(8):835-41. doi: 10.1002/jbmr.5650060808.
Clodronate (dichloromethylenebisphosphonate) decreased vasoconstriction of the isolated perfused rat tail artery mediated by norepinephrine and by Ca2+ in a K(+)-depolarizing solution. The norepinephrine contractile response was divided into two components by sequential manipulation of the composition of the perfusion fluid, where the first component is due to the release of Ca2+ from intracellular stores and the second to the influx of Ca2+ from extracellular fluid. Clodronate (20 microM) decreased only the first component of the response at a norepinephrine concentration of 50 nM, and both components of the response at a higher norepinephrine concentration (100 nM). The L-type Ca2+ channel blocking drugs, nicardipine (10 nM) and verapamil (1 microM), reduced the second component of the norepinephrine-mediated vasoconstriction, but in the presence of clodronate (20 microM) this blocking action was prevented. These results were confirmed by examining the interaction between clodronate and nicardipine on norepinephrine and K(+)-mediated lanthanum (La(3+)-resistant unidirectional 45Ca uptake. Nicardipine (1-10 nM) decreased the norepinephrine (100 nM) and K(+)-induced (60 mM) La(3+)-resistant unidirection 45Ca uptake in a concentration-dependent manner, but in the presence of clodronate (20 microM) this concentration-dependent response was abolished. Thus, clodronate not only reduced agonist-induced Ca2+ release from intracellular stores and Ca2+ influx through L-type Ca2+ channels but also prevented L-type Ca2+ channel antagonists from exerting their effect. These results indicate clodronate has two sites of action during vascular smooth muscle contraction: the first on intracellular mobilization of Ca2+ and the second on L-type Ca2+ channels.
氯膦酸盐（二氯亚甲基双膦酸盐）可降低去甲肾上腺素和钾离子去极化溶液中钙离子介导的离体灌注大鼠尾动脉的血管收缩。通过依次改变灌注液成分，去甲肾上腺素的收缩反应可分为两个部分，其中第一部分是由于细胞内钙库释放钙离子，第二部分是由于细胞外液钙离子内流。氯膦酸盐（20微摩尔）仅在去甲肾上腺素浓度为50纳摩尔时降低反应的第一部分，而在较高去甲肾上腺素浓度（100纳摩尔）时降低反应的两个部分。L型钙离子通道阻滞剂尼卡地平（10纳摩尔）和维拉帕米（1微摩尔）可降低去甲肾上腺素介导的血管收缩的第二部分，但在氯膦酸盐（20微摩尔）存在时，这种阻断作用被阻止。通过研究氯膦酸盐和尼卡地平对去甲肾上腺素和钾离子介导的镧（La(3+)抗性单向45Ca摄取的相互作用，证实了这些结果。尼卡地平（1-10纳摩尔）以浓度依赖的方式降低去甲肾上腺素（100纳摩尔）和钾离子诱导（60毫摩尔）的La(3+)抗性单向45Ca摄取，但在氯膦酸盐（20微摩尔）存在时，这种浓度依赖性反应被消除。因此，氯膦酸盐不仅减少激动剂诱导的细胞内钙库钙离子释放和通过L型钙离子通道的钙离子内流，还阻止L型钙离子通道拮抗剂发挥其作用。这些结果表明氯膦酸盐在血管平滑肌收缩过程中有两个作用位点：第一个作用于细胞内钙离子动员，第二个作用于L型钙离子通道。
