Effect of ipriflavone on bone changes induced by calcium restricted, vitamin D deficient diet in rats.

The preventive effect of ipriflavone, 7-isopropoxy-isoflavone, on the development of experimental osteopenia in rats was studied. Male Wistar rats (4 weeks old) on a calcium restricted, vitamin D deficient diet were given a daily oral administration of ipriflavone. The administration of ipriflavone (100 mg/kg BW/day) for 40 days significantly inhibited a decrease in the cortical thickness (14.0 +/- 1.6 vs. 17.1 +/- 2.9%, mean +/- SD, p less than 0.05) and bone calcium content (62 +/- 4 vs. 67 +/- 2 mg, p less than 0.05) in the femora of rats induced by a mild calcium restricted (0.3%), vitamin D deficient diet. This compound did not affect serum calcium levels in this condition. But a dose of 20 mg/kg BW/day of ipriflavone was insufficient to inhibit a decrease in bone calcium content. In rats fed on a more severe calcium restricted (0.03%), vitamin D deficient diet, the administration of ipriflavone (100 mg/kg BW/day) did not significantly affect the cortical thickness or calcium content. Intestinal calcium absorption measured by the in situ loop method was not significantly different between rats fed with a severe calcium restricted (0.03%), D deficient diet with or without ipriflavone (20 or 100 mg/kg BW/day) These results demonstrate that the new compound, ipriflavone, partially prevents bone calcium loss induced by a mild calcium restricted (0.3%), vitamin D deficient diet in rats. However, the precise mechanism of action of this compound remains unknown.