Vitamin A Supplementation Increases the Uptake of Chylomicron Retinyl Esters into the Brain of Neonatal Rats Raised under Vitamin A-Marginal Conditions1–3

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The most rapid phase of brain development occurs during the neonatal period. Vitamin A (VA; retinol) is critical for many aspects of this process, including neurogenesis, synaptic plasticity, learning, and memory formation. However, the metabolism of retinol in the neonatal brain has not been extensively explored.


We examined the uptake of VA into the brain in neonatal rats raised under VA-marginal conditions (control group) and assessed the effect of VA supplementation on the uptake of VA into the brain.


Sprague-Dawley neonatal rats (n = 104) nursed by mothers fed a VA-marginal diet were randomly assigned and treated on postnatal day 4 with an oral dose of either VA (6 μg retinyl palmitate/g body weight) or canola oil as the control, both of which contained 1.8 μCi [3H]retinol. Pups (n = 4/group at a time) were killed at 13 sampling times from 30 min to 24 d after dosing. The uptake of total retinol, chylomicron-associated retinyl esters (REs), and retinol bound to retinolbinding protein (RBP) was estimated with the use of WinSAAM version 3.0.8.


Total retinol mass in the brain was closely dependent on its mass in plasma over time (r = 0.91; P < 0.001). The uptake of retinol into the brain involved both postprandial chylomicrons and RBP, with RBP delivering most of the retinol in the control group [0.27 nmol/d (RBP) compared with 0.01 nmol/d (chylomicrons)]. VA supplementation increased the fractional uptake of chylomicron REs from 0.3% to 1.2% of plasma pool/d, decreased that of RBP retinol from 0.5% to 0.2% of plasma pool/d, and increased the transfer rate of chylomicron REs from nearly zero to 0.7 nmol/d, causing a daylong elevation in the brain mass of total retinol.


Postprandial chylomicrons may be a primary mechanism for delivering a recently ingested large dose of VA to the brain of neonatal rats raised under VA-marginal conditions.

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