Glycosaminoglycan stimulation of calcium release from mouse calvariae. Specificity for hyaluronic acid and dermatan sulfate

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Abstract
Heparin in combination with suboptimal concentrations of parathyroid hormone (PTH) has been shown to stimulate calcium release from bone organ cultures. The mechanism of action of heparin, however, is not known. One possible mechanism relates to the highly sulfated structure of heparin. We have compared heparin to other glycosaminoglycans to stimulate calcium release from mouse calvarial organ cultures in the presence and absence of suboptimal concentrations of parathyroid hormone. The exogenous addition of heparin to bone cultures demonstrated only slight effects on calcium release at 5.0, 10, and 100 μg/ml. The addition of hyaluronic acid to the calvarial cultures caused a significant release of calcium at 10 and 100 μg/ml compared to 5 μg/ml hyaluronic acid. Dermatan sulfate was equally as effective as hyaluronic acid at 100 μg/ml but not at 10 μg/ml. A comparison of heparin- and hyaluronic acid-stimulated release demonstrated a significantly greater amount of calcium release with hyaluronic acid 100 μg/ml. At 5.0 and 10 μg/ml, there was no difference between heparin and hyaluronic acid in the amount of calcium released into the culture medium. When heparin was added to the organ cultures with suboptimal concentrations of PTH, there was a significant enhancement of calcium release observed with 10 and 100 μg/ml heparin compared to heparin addition alone. When hyaluronic acid was added with suboptimal concentrations of PTH, no significant enhancement of calcium release was observed with 100 μg/ml hyaluronic acid. Dermatan sulfate, chondroitin sulfates A and C, and keratan sulfate, in combination with PTH, stimulated significant calcium release compared to the glycosaminoglycan added alone. These results indicate that heparin is not a specific glycosaminoglycan stimulator of calcium release from mouse organ culture and that other glycosaminoglycans are more effective both alone and in combination with PTH.