Modulation of absorption of beta-carotene and tissue accumulation of beta-carotene and vitamin A by different surfactants in rats.

BACKGROUND/AIMS: The absorption of beta-carotene is closely associated with the absorption of dietary fats in the duodenum. Aim of the study was to evaluate two different surfactants, taurocholate and Pluronic L-81, which are known to stimulate or inhibit the absorption of dietary fats, respectively with regard to the absorption of beta-carotene and tissue accumulation of beta-carotene and vitamin A.

METHODS

Rats were kept on a vitamin-A- deficient diet for 4 weeks and then either kept on this diet or fed this diet enriched with beta-carotene (200 mg/kg feed) alone or in combination with taurocholate (10 g/kg) or Pluronic L-81 (5 ml/kg) for another two weeks.

RESULTS

beta-carotene was not detectable in liver or plasma of rats fed the deficient diet. The supplementation of beta-carotene alone led to an increase of beta-carotene in plasma and organs (p < 0.05) and resulted in an increase of vitamin A in the liver (p < 0.01), indicating its conversion. The addition of taurocholate enhanced the absorption of beta-carotene (p < 0.01), but had little affect on the levels of total vitamin A in the liver. In contrast, Pluronic L-81 caused a reduced uptake of beta-carotene as indicated by lower concentrations in plasma and liver (p < 0.01) as well as reduced total vitamin A levels in the liver (p < 0.01) either caused by the reduced availability of beta-carotene or a reduced conversion into vitamin A.

CONCLUSIONS

The study shows that surfactants can modulate beta-carotene absorption differently. The results for taurocholate confirm known observations concerning an enhanced absorption of beta-carotene. Pluronic L-81 might diminish the uptake of beta-carotene into the enterocyte, which would be in disagreement with regard to its function in the absorption of total lipids in general, or might effect the excretion into the blood by modulation chylomicron secretion.