Chloroquine phosphate and the intestinal transport of estrogens

The effect of the antimalaria drug, chloroquine phosphate, on the transport of [3H]estradiol and [3H]estrone sulphate was studied in isolated sacs of rat duodenum. Net transport of the two estrogens from the mucosal to the serosal sides of the intestinal segment was significantly stimulated at chloroquine concentration of 1.0 mM or higher. However, the transformation of estradiol to estrone glucuronide and of estrone sulphate to estrone, which is normally associated with the transport of these estrogens, was significantly inhibited in the presence of the drug.