TISSUE DISTRIBUTION OF K-VITAMERS UNDER DIFFERENT NUTRITIONAL REGIMENS IN THE RAT

Two forms of vitamin K [phylloquinone (K-1) and menaquinone-4 (MK-4)] were added to vitamin K-deficient rat food in varying amounts, These d iets were given as the sole source of nutrition to rats for one week. The minimal dietary requirements (MDR) to attain maximal prothrombin s ynthesis were determined to be 0.6 and 6-10 mu g/g of food for K-1 and MK-4, respectively. The difference between both vitamers could be exp lained by the limited hepatic accumulation of MK-4. Next, vitamin K wa s offered to rats at concentrations ranging between 0.6 and 3000 mu g/ g of food, and the tissue distribution of vitamin K was investigated a fter one week of administration. Accumulation of K-1 and MK-4 was foun d in all tissues investigated, but both the absolute tissue concentrat ion and the ratio between K-1 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 i n pancreas and testis after a diet containing K-1 exclusively. The dat a indicate that this conversion is tissue-specific, but neither the re ason nor its mechanism are known. (C) 1998 Elsevier Science B.V.