PRENYLFLAVONOIDS - A NEW CLASS OF NONSTEROIDAL PHYTOESTROGEN (PART 2)- ESTROGENIC EFFECTS OF 8-ISOPENTENYLNARINGENIN ON BONE METABOLISM

In order to examine whether 8-isopentenylnaringenin (1), which has bee n proven to possess estrogen agonist activity in in vitro tests, also produces in vivo estrogenic properties, the effects of 1 on uterus and on bone metabolism were determined in ovariectomized rats. Rats were ovariectomized and treated with 1 at 30 mg/kg/day subcutaneously for t wo weeks or 17 beta-estradiol at 0.01 mg/kg/day subcutaneously for two weeks. Ovariectomy resulted in an increase in urinary excretion of bo ne resorption markers (hydroxyproline, pyridinoline and deoxypyridinol ine) and a decrease in bone mineral density of the proximal tibia as w ell as reduced uterine weight. Treatment with 1 or 17 beta-estradiol c ompletely suppressed these ovariectomy-induced bone and uterine change s in a qualitatively similar manner. These results demonstrate that 1 acts as an estrogen agonist in the uterus as well as in bone in vivo.