Ipriflavone, a synthetic phytoestrogen, enhances intestinal calcium transport in vitro

Ipriflavone (IP), a synthetic isoflavone, prevents bone loss associated with ovarian hormone deficiency in women and animal models. This protective effect of IP may be partly due to its ability to enhance calcium absorption. The purpose of this study was to examine the effects of IP and 17 beta-estradiol (E-2) on in vitro intestinal calcium transport in an ovariectomized rat model using E-2 as a positive control. Forty-eight 90-day-old female Sprague-Dawley rats were divided into four groups: one sham-operated (sham) and three ovariectomized groups. The ovx groups were either control (ovx), supplemented with IP (100 mg/kg body weight daily) via Savaging (ovx+IP), or injected with E-2 (10 mu g/kg body weight) (ovx+E-2). Animals were fed diets containing 0.4% calcium, 0.3% phosphorus, and 0.195 nmol vitamin D-3/g for 35 days from the date of surgery. Animals were exsanguinated, and isolated cells from the duodenum, jejunum, ileum, and colon were used to measure in vitro calcium uptake. Calcium uptake by duodenal cells was significantly greater in the IP and E-2-related animals compared with the ovx control group. In addition, calcium uptake by the ileal and colonic cells of the E-2-treated animals was significantly greater compared with all the other groups. The results confirm our earlier findings implicating a role for estrogen in duodenal calcium uptake. The findings also indicate that IP, although less potent than estrogen, significantly enhances calcium uptake in the duodenum, the active site of calcium absorption.