Abstract
In the previous paper, it was shown that the hepatic CoA value determined by Kaplan・Lipmann's method were reduced significantly by the administration of thiamine derivatives. In the present paper, the effects of excessive administration of thiamine tetrahydrofurfuryldisulfide (TTFD) on the concentrations of CoA, pantothenic acid and vitamin B_6 of rat liver were studied. The precursors of CoA, such as dephospho-CoA, phosphopantetheine or phosphopantothenoylcysteine, are included in CoA value determined by Kaplan・Lipmann's method, while Wakil's method is specific for CoA. When 500μg of TTFD was given orally for 2 weeks, the values of total pantothenic acid and CoA determined by Kaplan・Lipmann's method decreased markedly, while CoA value by Wakil's method and vitamin B_6 value by Atkin's method were unchanged compared with those of control. The value of total pantothenic acid returned to normal and those of CoA-precursors were recovered to 85% of normal by the administration of 5mg of pantothenic acid daily, but 1.5mg of vitamin B_6 had no influence on CoA and pantothenic acid. From these results, it is supposed that an excessive administration of thiamine derivatives causes a reduction of CoA-precursors owing to the inhibition of phosphorylation of pantothenic acid.
