Uptake and phosphorylation of thiamine in rat kidney cortical slices. I. Effect of ethanol.

Processes involved in the disposition of thiamine within the kidney were studied in rat kidney slices. Uptake of [14C]thiamine and its metabolism to [14C]thiamine phosphate were measured with and without the presence of ethanol. Whereas slice to medium ratios of 3.41 +/- 0.11 indicated uphill movement of [14C]thiamine, metabolism to [14C]thiamine phosphate provided a metabolic sink for movement of thiamine into the cell. Accumulation was saturable and associated, in part, with the formation of thiamine phosphate. Ethanol, at 25 mM, a concentration compatible with alcohol abuse, significantly (P < .001) decreased the maximal accumulation of [14C]thiamine from 210 +/- 12.7 to 115 +/- 4.2 nmol/g and the production of thiamine phosphate from 0.44 to 0.041 nmol/g. These data indicate a facilitated uptake of thiamine and a conversion to thiamine phosphate by the kidney. The effect of ethanol to decrease thiamine accumulation in kidney tissue is suggested to be at the phosphorylating step.