Malabsorption of Thiamin in Folate-deficient Rats

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Abstract
Sprague-Dawley weanling rats were rendered folate deficient by feeding a folate-free diet supplemented with succinylsulfathiazole for 3 or 10 months. These rats exhibited a ten- and fivefold reduction of liver and erythrocyte folate levels, respectively, at 3 months and 110-fold reduction of folate in these organs after 10 months, as compared with control animals. In the folate-deficient rats there was a significant (30 to 50%) decrease in duodenal and jejunal absorption of low doses of thiamin hydrochloride (0.5 µM), whereas high doses of thiamin (17.5 µM) were assimilated normally. This differential absorption of these two doses of thiamin is explained in terms of a dual absorptive mechanism for thiamin, active and saturable at low concentrations and passive at higher levels of thiamin. “Megaloblastic” changes were seen in the duodenum and jejunum, but not the ileum of folate-deficient rats. Two weeks of folate repletion restored the tissue folate levels essentially to normal and reversed the intestinal absorptive defect for thiamin, but the morphologic changes in the gut persisted.