HEPARIN FAILS TO POTENTIATE THE EFFECTS OF IL-1-BETA-MEDIATED BONE-RESORPTION OF FETAL-RAT LONG BONES IN-VITRO

Heparin has been identified as a potent modulator of bone resorption. Heparin induces osteoporosis during long-term administration and has b een shown in vitro to enhance the effects of other bone resorbing fact ors, including parathyroid hormone. In this study, we examined the eff ects of heparin on the bone-resorbing activity of the inflammatory cyt okine IL-1 beta. Resorption was determined by measuring release of pre viously incorporated Ca-45 from fetal rat long bones cultured in mediu m supplemented with either 0.1% bovine serum albumin or 10% heat-inact ivated fetal calf serum. Heparin, in the absence of serum, decreased b asal resorption at 4 and 10 units/ml, and slightly increased resorptio n at 30 units/ml. Heparin had no effect on IL-1 beta-stimulated resorp tion. In the presence of serum, heparin induced a two-fold increase in resorption alone, however, when cocultured with IL-1 beta, heparin fa iled to further enhance IL-1 beta-stimulated resorption.