Abstract
Incorporation of homopantothenic acid (HOPA) into the various tissues, especially into neurons in the brain was studied using the autoradiography after injection of ^3H-HOPA in mouse. Many grains of reduced silver were found in various parts of the brain 30minutes after the injection of ^3H-HOPA, and at that time the density of the grain was much higher in the neuropil than in the nerve cell bodies. The maximal incorporation rate of ^3H-HOPA into brain tissue was found at one hour after the injection, and the density of grains in the cytoplasm of neuron exceeded that of the neuropil. At three hours after injection, many grains still remained in the neurons, thereafter it decreased rapidly with the lapse of time, and disappeared throughout the brain at 12 hours after the injection. There was no remarkable difference in incorporation rates between various kinds of neurons. After 30minutes of the injection the grains were already detectable in urinary tubule cells. The excretion of ^3H-HOPA from kidney tissue appears to be very rapid. In the liver cells the amounts of the grains decreased rapidly at one hour after injection. ^3H-HOPA does not accumulate in liver cells.
