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Rat Intestinal ß-Carotene Dioxygenase Activity Is Located Primarily in the Cytosol of Mature Jejunal Enterocytes^1,2,

Christelle Duszka, Pascal Grolier^*, El-Mostafa Azim, Marie-Cécile Alexandre-Gouabau, Patrick Borel and Véronique Azais-Braesco

^* INRA, Unité des Maladies Métaboliques, 63122 Saint Genès Champanelle, France INSERM U71, 63005 Clermont-Ferrand, France

The purposes of this study were to determine the location of ß-carotene dioxygenase (EC 1.13.11.21) activity within the rat gastrointestinal tract, within the villus and within enterocytes, and to identify the metabolites produced in each intestinal fraction. In Wistar female rats, maximal activity was detected in the cytosol (74–93% of the total cellular activity) of mature functional enterocytes harvested from the jejunum (67% of the intestinal activity). The specific activity, expressed in pmol of retinoids/(h·mg protein) rose from 49 ± 3 in the stem cells to 199 ± 12 in the mature functional cells (P < 0.05). Thus the intestinal ß-carotene cleavage activity might be regulated during the enterocyte maturation process. By using HPLC with diode array and radioactive detectors, retinal, and in the presence of NAD⁺, retinoic acid, were identified as the only metabolites produced. No ß-12'-, 10'-, and 8'-apo-carotenals were detected, even when various enzyme sources were tested. These results suggest that the major, if not the sole, pathway for the formation of vitamin A from ß-carotene in the rat intestine is central cleavage.

KEY WORDS: • ß-carotene • vitamin A activity • enterocytes • rats

¹ Supported by a grant (92-G 0477) from the French Department of Research and Space.

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

Manuscript received 31 December 1995. Revision accepted 1 July 1996.

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