Ronden J E, Thijssen H H, Vermeer C
Department of Biochemistry, Cardiovascular Research Institute, Maastricht University, The Netherlands.
Biochim Biophys Acta. 1998 Jan 8;1379(1):16-22. doi: 10.1016/s0304-4165(97)00075-5.
Two forms of vitamin K [phylloquinone (K1) and menaquinone-4 (MK-4)] were added to vitamin K-deficient rat food in varying amounts. These diets were given as the sole source of nutrition to rats for one week. The minimal dietary requirements (MDR) to attain maximal prothrombin synthesis were determined to be 0.6 and 6-10 microg/g of food for K1 and MK-4, respectively. The difference between both vitamers could be explained by the limited hepatic accumulation of MK-4. Next, vitamin K was offered to rats at concentrations ranging between 0.6 and 3000 microg/g of food, and the tissue distribution of vitamin K was investigated after one week of administration. Accumulation of K1 and MK-4 was found in all tissues investigated, but both the absolute tissue concentration and the ratio between K1 and MK-4 were tissue-dependent. Highest values were found in liver and in heart, but since the heart contains no gamma-glutamylcarboxylase, the function of vitamin K in this tissue remains obscure. High tissue concentrations of MK-4 were also found in pancreas and testis after a diet containing K1 exclusively. The data indicate that this conversion is tissue-specific, but neither the reason nor its mechanism are known.
将两种形式的维生素K（叶绿醌（K1）和甲基萘醌-4（MK-4））以不同量添加到维生素K缺乏的大鼠食物中。这些饮食作为大鼠唯一的营养来源持续一周。达到最大凝血酶原合成的最低饮食需求量（MDR）经测定，K1和MK-4分别为0.6和6 - 10微克/克食物。两种维生素类似物之间的差异可以通过MK-4在肝脏中的有限积累来解释。接下来，以0.6至3000微克/克食物的浓度向大鼠提供维生素K，并在给药一周后研究维生素K的组织分布。在所研究的所有组织中均发现了K1和MK-4的积累，但绝对组织浓度以及K1与MK-4之间的比例均取决于组织。在肝脏和心脏中发现的值最高，但由于心脏不含γ-谷氨酰羧化酶，维生素K在该组织中的功能仍不清楚。在仅含K1的饮食后，胰腺和睾丸中也发现了高组织浓度的MK-4。数据表明这种转化具有组织特异性，但原因及其机制均未知。
