Abstract
Uptake of riboflavin-^<14>C (B_2-^<14>C) and riboflavin tetrabutyrate-^<14>C (B_2-But-^<14>C) in various organs of the mice with oral administration has been studied by microautoradiogram. Both B_2-^<14>C and B_2-But-^<14>C were absorbed from upper small intestine and brought into liver by portal vein. In the liver marked uptake of the vitamin was observed in cytoplasm and nucleus of liver cells. Grains found in the cytoplasm revealed diffuse distribution from cell membrane to nucleus or accumulation in Golgi field. Nuclear grains were detected in karyoplasm and nucleolus. Myocardium exhibited marked uptake of B_2-^<14>C and B_2-But-^<14>C in muscle fibers. Brain and spinal cord disclosed numerous grains in nerve cells. Perikaryon showed much grains, though less in nerve fibers. Hypophysis revealed uptake of the vitamin in glandular cells of anterior lobe. Thyroid gland showed uptake in follicular epthelium. Adrenal gland exhibited marked distribution of the grains in cortical cells, especially in fascicular zone. Marked uptake was detected in Langerhans' islets of pancreas. In the eyes the most marked uptake was demonstrated in pigment cell and layer of rods and cones of the retina. B_2-But-^<14>C showed distribution of the grains in the liver and brain for longer time than B_2-^<14>C.
