Inhibitory effect of inositol phosphates on parathyroid hormone-induced bone resorption in organ cultures

This study investigates the ability of phytic acid, its inositol phosphate derivatives (inositol penta-, tetra-, tri-, di-, and monophosphate), and inorganic phosphate to inhibit parathyroid hormone (PTH)-induced resorption of fetal rat long bones in organ culture. Pregnant rats injected with 45Ca on the 18th day of gestation were killed the next day and their fetuses removed. Half of each pair of dissected long bones was incubated in a chemically defined control medium, while the contralateral half was incubated in medium containing PTH or PTH plus the phosphate compound to be tested. 45Ca released into the medium was indicative of the amount of bone resorption. All phosphate compounds tested inhibited resorption. The inositol phosphates should be studied further to assess their suitability as therapeutic agents for treatment of metabolic bone diseases involving increased turnover.