Benzo(B)thiophene-2-carboxylic acid: calcium uptake and cyclic AMP production in isolated bone cells.

The purpose of the present study was to investigate the mechanism of action on bone of Benzo(B)Thiophene-2-Carboxylic Acid (BL-5583). BL-5583, at a dose range of 0.01-100 micrograms/ml, inhibited spontaneous as well as A23187 and PTH-induced bone resorption in tissue culture. This compound also decreased calcium uptake in both osteoclastic and osteoblastic enriched bone cell populations obtained by sequential collagenase digestion of 1-2 day newborn rat calvariae. The decrease occurred after a 5 min. incubation with 45Ca and BL-5583. The effective dose range was 0.01-100 micrograms/ml. No effect on leucine incorporation or lactic acid production by bone cells was observed. BL-5583 also induced a transient decrease in calcium uptake in skin cells isolated from fetal rats by collagenase digestion, suggesting a lack of tissue specificity for this compound. No effect on cyclic AMP in isolated bone cells was observed with the same dose range that produced a calcium effect.