VITAMIN-K DISTRIBUTION IN RAT-TISSUES - DIETARY PHYLLOQUINONE IS A SOURCE OF TISSUE MENAQUINONE-4

The present study was undertaken to determine whether there is selecti ve tissue distribution of vitamin K in the rat and whether this distri bution mirrors the distribution of tissue vitamin K metabolism. The ef fects of feeding a vitamin K-free diet followed by resupplementation w ith phylloquinone (K-1) were studied. K-1 was recovered in all tissues . In K-1-supplemented rats, most tissues accumulated K-1 relative to p lasma K-1 with the highest levels in liver, heart, bone, and cartilagi nous tissue (sternum). Loa K-1 levels were found in the brain. In the K-1-free rats, relatively high K-1 levels were still found in heart, p ancreas, bone and sternum. Surprisingly, menaquinone-4 (MK-4) was dete cted in all tissues, with low levels in plasma and liver, and much hig her levels in pancreas, salivary gland and sternum. MK-4 levels exceed ed K-1 levels in brain, pancreas, salivary gland and sternum. Suppleme ntation with K-1, orally and by intravenous infusion, caused MK-4 leve ls to rise. Some accumulation of K-1 and MK-4 in the mitochondrial fra ction was found for kidney, pancreas and salivary gland. In the liver the higher menaquinones (MK-6-9) accumulated in the mitochondria. The results indicate that: (1) there is selective tissue distribution of K -1 and MK-4, (2) dietary K-1 is a source of MK-4. The results also sug gest there may be an as yet unrecognized physiological function for vi tamin K (MK-4).