Vitamin A deficiency reduces uptake off beta-carotene by brush border membrane vesicles but does not alter intestinal retinyl ester hydrolase activity in the rat

Vitamin A deficiency has been reported to result in mild structural and fun ctional changes within the small intestine. The objective of this study was to measure the impact of vitamin A deficiency in the rat on several functi onal aspects of beta -carotene uptake and intestinal retinyl ester hydrolys is. These included uptake of C-14-beta -carotene by brush border membrane v esicles (BBMV) and in vitro activity of intrinsic retinyl ester hydrolase ( REH). Rats (n = 33) were randomly assigned to receive one of three dietary treatments: vitamin A deficient (-VA), vitamin A sufficient pair-fed (PF), or vitamin A sufficient free access-fed (FA). Liver, serum retinol, and gro wth data were used to verify clinical vitamin A deficiency. Rats in the -VA group were clinically vitamin A deficient by Day 56 on a vitamin A-free di et and, at that point, all rats were randomly assigned to one of two experi mental treatments: BBMV studies or REH activity assays. Uptake of C-14-beta -carotene by BBMV was significantly suppressed (P < 0.05) in -VA rats when compared to both PF and FA control rats during early passive uptake equili bration (10-20 sec). Uptake was also significantly decreased by BBMV isolat ed from -VA rats compared to PF controls, but not FA controls, after a 10-m in incubation (P < 0.05). In vitro activity of REH was not impacted by vita min A deficiency in rats, although a trend for greater activity from -VA ra ts was noted. These data suggest that vitamin A deficiency impairs enterocy te membrane uptake of beta -carotene without altering the enzymatic activit y of intrinsic REH. (J. Nutr. Biochem. 11:436-442, 2000) (C) Elsevier Scien ce Inc. 2000. All rights reserved.