Thomsen M K, Wildgoose P, Nilsson P, Hedner U
Biopharmaceuticals Division, Novo Nordisk A/S, Gentofte, Denmark.
Pharmacol Toxicol. 1993 Sep;73(3):127-32. doi: 10.1111/j.1600-0773.1993.tb01549.x.
The vitamin K-dependent clotting factors II, VII, IX, and X are proteins which undergo gamma-carboxylation of specific glutamic acid residues prior to secretion from the liver. These unique Ca2+ binding amino acids allow the interaction of the proteins with cell surface phospholipids, a function that is crucial for expression of full procoagulant activity of the proteins. The N-terminal region of the molecule contains the gamma-carboxylation sites and is termed the Gla-domain. A preliminary observation in rats suggested that mineralized bone accumulated activated recombinant FVII (rFVIIa: NovoSeven) as well as the non-activated, single chain rFVII. The present study investigated the role of the Gla-domain in the accumulation of rFVII in bone, as well as the influence of the activation state of FVII on this phenomenon. Rats were treated with 125I-labelled rFVII, rFVIIa, Gla-domainless rFVIIa, factor IX, iodide, or recombinant human growth hormone (rhGH). Following sacrifice, radioactivity was measured in mineralized bone, among other tissues. Following administration of 125I-radiolabelled rFVII, rFVIIa and factor IX, but not Gla-domainless rFVIIa, iodide or rhGH, extensive sequestration occurred in endochondrally as well as intramenbranously ossified bones. The results indicate that the proteins containing a Gla-domain, and only these, are sequestered in bone. Additionally, the normally occurring form of FVII in the circulation, the single-chain FVII, exhibited similar kinetics in rat bone and plasma, as the two-chain rFVIIa. The half-life of rFVII/rFVIIa in mineralized bone was between 3 and 4 days, implying that significant bone accumulation of the factor will take place at steady state.(ABSTRACT TRUNCATED AT 250 WORDS)
维生素K依赖的凝血因子II、VII、IX和X是在从肝脏分泌之前特定谷氨酸残基会发生γ羧化的蛋白质。这些独特的钙离子结合氨基酸使这些蛋白质能够与细胞表面磷脂相互作用，这一功能对于这些蛋白质充分发挥促凝血活性至关重要。分子的N端区域包含γ羧化位点，被称为Gla结构域。对大鼠的初步观察表明，矿化骨会蓄积活化的重组FVII（rFVIIa：诺其）以及未活化的单链rFVII。本研究调查了Gla结构域在rFVII于骨中蓄积过程中的作用，以及FVII的活化状态对这一现象的影响。给大鼠注射125I标记的rFVII、rFVIIa、无Gla结构域的rFVIIa、因子IX、碘化物或重组人生长激素（rhGH）。处死后，在矿化骨以及其他组织中测量放射性。注射125I标记的rFVII、rFVIIa和因子IX后，而非无Gla结构域的rFVIIa、碘化物或rhGH后，在软骨内以及膜内骨化骨中均发生了广泛的滞留。结果表明，只有含有Gla结构域的蛋白质才会滞留在骨中。此外，循环中正常存在的FVII形式，即单链FVII，在大鼠骨和血浆中的动力学与双链rFVIIa相似。rFVII/rFVIIa在矿化骨中的半衰期在3至4天之间，这意味着在稳态时该因子会在骨中大量蓄积。（摘要截断于250字）
