Effects of KCA-012 on bone metabolism in organ culture.

3,9-Dihydroxy-5H-benzofuro[3,2-c]quinoline-6-one (KCA-012), the chemical structure of which is closely similar to that of the phytoestrogen coumestrol, inhibited parathyroid hormone-, 1 alpha,25-dihydroxyvitamin D3- and prostaglandin E2-induced bone resorption of cultured fetal rat bones. KCA-012 also increased the calcium content of 9-day chick embryonic femur cultured in vitro. KCA-012 did not show any estrogenic activity as determined by an increase in the uterine weight of ovariectomized rats, whereas coumestrol did. These results indicate that KCA-012 has no estrogenic activity and has unique effects of inhibiting bone resorption and stimulating bone mineralization.