The effect of vitamin A status on the uptake of β-carotene into Mongolian gerbil brush border membrane vesicles

Brush border membrane vesicles (BBMV) have previously been used to investigate the absorptive processes of a wide variety of nutrients. We successfully developed a BBMV system to study the uptake of betacarotene (BC) using adult female rat small intestine. Time course assays demonstrated passive uptake of all-trans BC by BBMV. This method was used to evaluate the effects of vitamin A (VA) status on BC uptake by BBMV in three groups of Mongolian gerbils, a species that absorbs BC intact. One group of gerbils (A, n=10) was fed a VA deficient diet for 8 weeks, a second group (B) was refed VA for 5 days following the 8 week period and the third (C) was further depleted of VA for 5 additional days. After 8 weeks, hepatic concentrations of VA indicated that the gerbils were in a marginally deficient state. The BBMV isolated from the proximal small intestine of each group were pooled and incubated with bile acid micelles containing all-trans BC. The uptake of BC by the BBMV was followed for 20 minutes. Group A (marginally deficient) had a significantly greater uptake of BC when compared to the refed group B (p=.0001), which, in turn had a significantly greater uptake than the more deficient group C (p=.0001). Reduced uptake by the most deficient animals may be due to decreased mucosal cell membrane integrity that accompanies VA deficiency. These results suggest that as animals become VA deficient there may be impairment of BC uptake by intestinal mucosal cells.