Mallik Rangan, Yoo Michelle J, Chen Sike, Hage David S
Department of Chemistry, University of Nebraska, Lincoln, NE 68588-0304, USA.
J Chromatogr B Analyt Technol Biomed Life Sci. 2008 Dec 1;876(1):69-75. doi: 10.1016/j.jchromb.2008.10.022. Epub 2008 Oct 21.
The binding of verapamil to the protein human serum albumin (HSA) was examined by using high-performance affinity chromatography. Many previous reports have investigated the binding of verapamil with HSA, but the exact strength and nature of this interaction (e.g. the number and location of binding sites) is still unclear. In this study, frontal analysis indicated that at least one major binding site was present for R- and S-verapamil on HSA, with estimated association equilibrium constants on the order of 10(4)M(-1) and a 1.4-fold difference in these values for the verapamil enantiomers at pH 7.4 and 37 degrees C. The presence of a second, weaker group of binding sites on HSA was also suggested by these results. Competitive binding studies using zonal elution were carried out between verapamil and various probe compounds that have known interactions with several major and minor sites on HSA. R/S-Verapamil was found to have direct competition with S-warfarin, indicating that verapamil was binding to Sudlow site I (i.e. the warfarin-azapropazone site of HSA). The average association equilibrium constant for R- and S-verapamil at this site was 1.4 (+/-0.1)x10(4)M(-1). Verapamil did not have any notable binding to Sudlow site II of HSA but did appear to have some weak allosteric interactions with l-tryptophan, a probe for this site. An allosteric interaction between verapamil and tamoxifen (a probe for the tamoxifen site) was also noted, which was consistent with the binding of verapamil at Sudlow site I. No interaction was seen between verapamil and digitoxin, a probe for the digitoxin site of HSA. These results gave good agreement with previous observations made in the literature and help provide a more detailed description of how verapamil is transported in blood and of how it may interact with other drugs in the body.
采用高效亲和色谱法研究了维拉帕米与人血清白蛋白（HSA）的结合情况。此前已有许多报道研究了维拉帕米与HSA的结合，但这种相互作用的确切强度和性质（如结合位点的数量和位置）仍不清楚。在本研究中，前沿分析表明，在pH 7.4和37℃条件下，HSA上至少存在一个R-和S-维拉帕米的主要结合位点，其估计的缔合平衡常数约为10⁴M⁻¹，维拉帕米对映体的这些值相差1.4倍。这些结果还表明HSA上存在第二组较弱的结合位点。使用区域洗脱进行了维拉帕米与各种已知与HSA上几个主要和次要位点有相互作用的探针化合物之间的竞争性结合研究。发现R/S-维拉帕米与S-华法林存在直接竞争，表明维拉帕米与Sudlow位点I（即HSA的华法林-阿扎丙宗位点）结合。该位点上R-和S-维拉帕米的平均缔合平衡常数为1.4（±0.1）×10⁴M⁻¹。维拉帕米与HSA的Sudlow位点II没有明显结合，但似乎与该位点的探针l-色氨酸有一些弱的变构相互作用。还注意到维拉帕米与他莫昔芬（他莫昔芬位点的探针）之间存在变构相互作用，这与维拉帕米在Sudlow位点I的结合一致。未观察到维拉帕米与HSA地高辛位点的探针地高辛之间有相互作用。这些结果与文献中先前的观察结果高度一致，有助于更详细地描述维拉帕米在血液中的转运方式以及它在体内与其他药物可能的相互作用方式。
