The role of vitamin A status in the conversion of all-trans retinoyl β-glucuronide to retinoic acid in male Sprague-Dawley rats

Orally administered all-trans retinoyl beta-glucuronide, after its absorption from the intestine, is distributed widely in the tissues, except for brain, of both vitamin A-sufficient (A+) and vitamin A-deficient (A-) rats. Although the digestion and rate of absorption of retinoyl beta-glucuronide are similar in A+ and A- rats, the rates of hydrolysis of retinoyl beta-glucuronide to retinoic acid markedly differ. Thus, after an oral dose (6.3 mu mol) of all-trans retinoyl beta-glucuronide in corn oil, retinoic acid peaks at 4 hr in the plasma at a concentration of 2.5 to 4.2 mu M in A- rats, up to 40-fold higher than in A+ rats. The peak retinoic acid concentration in A- rats increased with the severity of the deficiency. Similarly, the ratio of retinoic retinoic acid/retinoyl beta-glucuronide in various tissues of A- rats is 1.3 to 12.5-fold higher than in those of A+ rats. In the absence in tissues of retinol or its ester, A- rats clearly use administered retinoyl beta-glucuronide as a ready source of retinoic acid. (C) Elsevier Science Inc. 1998.