Vitamin K Distribution in Rat Liver and Heart Muscle and Some Metabolic Properties

Abstract

Intracellular distribution and some additional studies of metabolic fate of vitamin K homologs were studied by isotopic tracer with tritium or carbon-14 labeled vitamin K homologs, vitamin K₁, K₂₍₂₀₎ and K₃, to obtain the information about their site of action in the animal tissue. There are several reports on the intracellular distribution of K₁ but no clear result has been obtained about the incorporation site of vitamin K₁ in the animal cell and no report has been found in the case of K₂₍₂₀₎, which is estimated to be a physiologically active type of K homologs in the animal. In our present experiment, K₁ was found to be concentrated in the mitochondrial fraction after a long period of time and K₂₍₂₀₎ was faster incorporated in the liver and heart muscle than K₁ and showed remarkably higher affinity to the mitochondrial fraction. K₃ which is less lipophilic than the other two homologs, was less incorporated into the both tissues and stayed in the supernatant fraction. From these observations, it was revealed that K₁ and K₂ which have a long isoprenoid side chain have a higher mitochondrial affinity like other isoprenoid vitamins and the higher affinity of vitamin K to the mitochondrial fraction suggest the possibility of their function in some regulation process in mitochondria other than blood coagulation protein synthesis.