[Tissue distribution of vitamin B12 and its dynamics in nervous tissues]

Tissue distributions and intracellular localization of vitamin B12 (abbr B12) were described in spinal cords, roots and peripheral nerves of humans. The followings are results. 1) B12 contents of spinal cords are found to increase with centripetal slope. 2) Higher contents of B12 were found in ventral horn than lateral and posterior columns. 3) Motor nerves contained higher B12 contents than sensory nerves. 4) Considerable amounts of cyano-B12 was main component among B12-derivatives in nerve tissues. 5) Intracellular B12 was rich in mitochondrial fraction. 6) By ligation of sciatic nerves, B12 bound to nerves was released from nerve tissues and cyanide ions were later released, though its mechanisms remains unknown.