Intestinal flora is not an intermediate in the phylloquinone-menaquinone-4 conversion in the rat

Biochim Biophys Acta. 1998 Jan 8;1379(1):69-75. doi: 10.1016/s0304-4165(97)00089-5.


To elucidate the role of intestinal bacteria in the conversion of phylloquinone into menaquinone-4 (MK-4) we investigated the tissue distribution of vitamin K in germ-free rats. The rats were made vitamin K deficient by feeding a vitamin K-free diet for 13 days. In a subsequent period of 6 days, phylloquinone and menadione were supplied via the drinking water in concentrations of 10 and 50 micromol l(-1). Menadione supplementation led to high levels of tissue MK-4, particularly in extrahepatic tissues like pancreas, aorta, fat and brain. Liver and serum were low in MK-4. Phylloquinone supplementation resulted in higher phylloquinone levels in all tissues when compared with vitamin K-deficient values. The main target organs were liver, heart and fat. Remarkably, tissue MK-4 levels were also higher after the phylloquinone supplementation. The MK-4 tissue distribution pattern after phylloquinone intake was comparable with that found after menadione intake. Our results demonstrate that the conversion of phylloquinone into MK-4 in extrahepatic tissues may occur in the absence of an intestinal bacterial population and is tissue specific. A specific function for extrahepatic MK-4 or a reason for this biochemical conversion of phylloquinone into MK-4 remains unclear thus far.

MeSH terms

  • Animals
  • Diet
  • Germ-Free Life*
  • Intestines / microbiology*
  • Male
  • Rats
  • Rats, Wistar
  • Vitamin K / analogs & derivatives*
  • Vitamin K / analysis*
  • Vitamin K / biosynthesis
  • Vitamin K / metabolism
  • Vitamin K 1 / analysis
  • Vitamin K 1 / metabolism*
  • Vitamin K 2 / analogs & derivatives
  • Vitamin K Deficiency


  • Vitamin K 2
  • Vitamin K
  • menatetrenone
  • Vitamin K 1