Effect of chronic ethanol administration on thiamine transport in microvillous vesicles of rat small intestine.

The effect of long-term ethanol administration on the membrane mechanism of thiamine entry in rat enterocytes was investigated by using microvillous vesicles of small intestine. Experiments were carried out in three groups of Wistar albino rats of both sexes (290-400 g of initial body wt). Group I did not receive any treatment, group II received 4.7 g of ethanol/kg body wt (as a 50% hydroalcoholic solution) daily by gastric gavage for 35 days and group III (pair-fed controls) received a daily solution of saccharose (isoenergetic with the dose of ethanol administered to group II) by gastric gavage for 35 days. Ethanol or saccharose were administered in the morning and a standard diet was given throughout the treatment period. All animals were killed by decapitation 24 hr after the last administration, when the blood level of ethanol was virtually zero. Microvillous small intestinal vesicles were incubated with 3H-thiamine (3H-T) at 25 degrees C and the amount of 3H-T taken up was measured by a rapid filtration method. Compared with data obtained in groups I and III, chronic ethanol administration was found to induce a statistically significant decrease in 3H-T vesicular uptake at 4 sec (determined at 3H-T concentrations ranging from 0.12 to 7.5 microM) and a decrease in the apparent Jmax (maximal transport rate) value of the saturable component, without affecting the apparent Km (half-saturation concentration) value. These results indicate that in rats chronic ethanol administration may impair the intestinal absorption of thiamine by reducing thiamine entry into the enterocyte.