Govers-Riemslag José W P, Castoldi Elisabetta, Nicolaes Gerry A F, Tans Guido, Rosing Jan
Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, The Netherlands.
Thromb Haemost. 2002 Sep;88(3):444-9.
Carriership of the factor V (FV) R2 haplotype is associated with mild APC-resistance, moderately reduced FV levels and a relative increase of the more thrombogenic FV isoform, FV1. Since low FV levels and increased FV1 can theoretically cause APC-resistance, we investigated whether these alterations can quantitatively account for R2-associated APC-resistance. In order to determine the effect of FV concentration and FV isoform composition on the APC-response, we reconstituted FV-deficient plasma with purified FV1 and FV2 in different molar ratios and to varying FV concentrations. APC sensitivity ratios (APCsr) were determined with the Coatest APC Resistance V, which probes the effect of APC on both FVa- and FVIIIa-inactivation, and with the Immunochrom APC response test, which only quantifies the effect of APC on FVIII(a)-inactivation. In both assays, low FV concentrations and/or high relative amounts of FV1 rendered plasma samples more resistant to APC. APCsr were also determined in FV-deficient plasma reconstituted with purified FV at levels and isoform ratios observed in R2-homozygotes (98% FV, 42% FV1) and age-matched controls (119% FV, 26% FV1). In both tests the APCsr of reconstituted control plasma was the same as that of plasma from controls, whereas reconstituted R2-plasma was less APC-resistant than plasma from homozygous carriers of the R2 haplotype. We conclude that the low FV levels and altered FV isoform ratio cannot fully explain R2-associated APC-resistance.
因子 V（FV）R2 单倍型的携带与轻度活化蛋白 C（APC）抵抗、FV 水平适度降低以及更具血栓形成性的 FV 异构体 FV1 的相对增加有关。由于低 FV 水平和 FV1 增加理论上可导致 APC 抵抗，我们研究了这些改变是否能定量解释与 R2 相关的 APC 抵抗。为了确定 FV 浓度和 FV 异构体组成对 APC 反应的影响，我们用不同摩尔比的纯化 FV1 和 FV2 以及不同的 FV 浓度重构 FV 缺乏的血浆。使用检测 APC 对 FVa 和 FVIIIa 失活作用的 Coatest APC Resistance V 和仅定量 APC 对 FVIII(a)失活作用的免疫层析 APC 反应试验来测定 APC 敏感性比值（APCsr）。在这两种试验中，低 FV 浓度和/或高相对量的 FV1 使血浆样本对 APC 的抵抗性更强。还在以 R2 纯合子（98% FV，42% FV1）和年龄匹配对照（119% FV，26% FV1）中观察到的水平和异构体比例用纯化 FV 重构的 FV 缺乏血浆中测定了 APCsr。在这两种试验中，重构对照血浆的 APCsr 与对照血浆的相同，而重构的 R2 血浆对 APC 的抵抗性低于来自 R2 单倍型纯合携带者的血浆。我们得出结论，低 FV 水平和改变的 FV 异构体比例不能完全解释与 R2 相关的 APC 抵抗。
