17 beta-estradiol inhibition of ascorbic acid accumulation in human intestinal Caco-2 cells

We investigated the effect of estrogen on the accumulation of ascorbic acid by human intestinal Caco-2 cells. 17 beta-estradiol, synthetic estrogen di ethylstilbestrol, and partial agonist tamoxifen were found to inhibit ascor bic acid accumulation in a dose-dependent fashion. The inhibitory effect of estrogens can be observed at as short as 5 min of incubation. An additive effect was observed when they were used in combination. Similar to dietary flavonoids, inhibition was also observed in two other intestinal cell lines , HT-29 and IEC-6. These chemicals affected both Na+-dependent and Na+-inde pendent (K+ substituting Na+) accumulation of ascorbic acid and did not aff ect the efflux of accumulated ascorbic acid. Kinetic analysis of diethylsti lbestrol showed a non-competitive inhibition with an apparent K-i of 23 mu M. The hormone-ascorbic acid interaction in the intestinal cell could help to explain the known reduction in blood ascorbic acid level among oral cont raceptive users and female guinea pigs given contraceptive hormones. (C) 19 98 Elsevier Science B.V. All rights reserved.