Effect of Estrogen (Estinyl) on Ascorbic Acid Metabolism

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This study was designed to investigate the effects of synthetic estrogen on the metabolism of ascorbic acid in adult female guinea pigs. The animals were maintained on an ascorbic acid-free diet ad libitum. Oral administration of estrogen (estinyl, 5μg) in combination with 5mg of ascorbic acid daily for 21 days resulted in a significant decrease in plasma, liver, adrenal, and urinary concentrations of ascorbic acid, compared with those of the animals receiving only 5mg of the vitamin. Using [¹⁴C]ascorbic acid, the rate of exhalation of CO₂ appeared to be markedly higher in animals receiving ascorbic acid alone than in animals given the vitamin simultaneously with estrogen. The bioavailability of ascorbic acid during the first 300min was reduced by 25% following concomitant administration of estrogen. Furthermore, in animals receiving ascorbic acid plus estrogen, fecal levels of the vitamin were significantly higher than the controls receiving ascorbic acid alone. These observations indicate that estrogen-associated decreased levels of ascorbic acid in plasma, tissues, and urine may be due to impairment of the gastrointestinal absorption of the vitamin.