Urinary retinol excretion in marginally vitamin a deficient rats during inflammation and following supplementation with oil or water-miscible vitamin a

To assess whether urinary retinol excretion is due to inflammation or to other causes, vitamin A-marginal and -sufficient rats (4/ group) were treated i.p. with 50 μg of lipopolysaccharide (LPS) from P. aeruginosa/ 100 g of b.w. In a second experiment, 16 marginal rats were treated with LPS or saline, followed six hours later by an oral dose of 2 mg of retinol as oilsoluble (OILVA) or water-miscible (AQUVA) retinyl palmitate (four groups: OILVA alone, AQUVA alone, LPS+OILVA and LPS+AQUVA). Total plasma retinol was determined by HPLC before and 24 h post-treatment, and urinary retinol after 24 h collection. Inflammation with LPS caused hyporetinemia (∼40% reduction in plasma retinol) in both marginal and sufficient rats. However, in none of marginal LPS treated rats was retinol detected in urine (< 4.0 ng/dl), while among sufficient, only one rat excreted measurable retinol. Vitamin A supplementation increased total plasma retinol (∼2 times pre-treatment levels) in each of the four groups. However, urinary retinol was excreted by 50% of rats receiving AQUVA alone (range, 80 to 90 ng/dl) and 100% of those treated with LPS+AQUVA (range, 30 to 320 ng/dl). These results indicate that urinary retinol excretion is not necessarily associated with inflammation, and suggest that AQUVA differs metabolically from OILVA.