Lecithin:Retinol Acyltransferase Expression Is Regulated by Dietary Vitamin A and Exogenous Retinoic Acid in the Lung of Adult Rats

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Abstract
Lecithin:retinol acyltransferase (LRAT), a retinol esterifying enzyme, plays a major role in the metabolism and storage of vitamin A in several animal tissues. Groups of vitamin A (VA)-adequate (control) and VA-deficient rats were treated with vehicle or 5 mg of all-trans-retinoic acid (RA); an additional group of VA-deficient rats were fed 100 μg of RA. In control rats, lung LRAT mRNA and LRAT specific activity were ∼50% of the levels expressed in the liver. In the lung of VA-deficient rats, LRAT mRNA and specific activity levels were μg RA increased lung LRAT mRNA (P < 0.005) and specific activity (P < 0.0001), and treatment with 5 mg of RA increased LRAT mRNA level and specific activity more than ∼15- and 6-fold above those in control lung, respectively (both P ≤ 0.001). The lung tissue of VA-adequate rats contained retinyl ester (∼3 nmol/g tissue), whereas none was detected in the lung tissue of VA-deficient rats. These results show that LRAT expression and vitamin A storage are regulated by vitamin A status and by treatment with all-trans-RA in the adult lung. These results suggest that the regulated storage of vitamin A may be important for maintaining the integrity and physiologic functions of the lung.