title: Effects of phosphate on calcium release, lysosomal enzyme activity in the medium, and osteoclast morphometry in cultured fetal rat bones.
abstract: The relationship between changes in medium phosphate concentration and three indices of cell-mediated resorption in fetal rat bone cultures--calcium release, the activity of the lysosomal enzyme beta-glucuronidase in the medium, and the morphology of osteoclasts--has been investigated. Bones treated with either 1 mM or 4 mM phosphate, with or without parathyroid hormone, were examined. After 2 h of culture we found the predominant effect of changes in medium phosphate to be on non-cell-mediated resorption. However, after 24 h changes in medium phosphate affected both cell-mediated and non-cell-mediated resorptive mechanisms. The 24 h effects of phosphate were not associated with either a change in the activity of beta-glucuronidase in the medium or in the area of the ruffled border of osteoclasts, but 4 mM phosphate did prevent parathyroid hormone from increasing the area of the clear zone of osteoclasts. These results imply that changes in medium phosphate alter cell-mediated resorption by affecting mechanisms that are independent of increases in beta-glucuronidase activity or changes in the ruffled border of osteoclasts but that may involve effects on the clear zone of osteoclasts.
mesh_terms: D000818:Animals; D001862:Bone Resorption / Q000187:drug effects*; D001842:Bone and Bones / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D003470:Culture Media / Q000032:analysis; D005333:Fetus; D005966:Glucuronidase / Q000032:analysis; D008247:Lysosomes / Q000201:enzymology; D009924:Organ Culture Techniques; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects*; D010281:Parathyroid Hormone / Q000494:pharmacology; D010710:Phosphates / Q000494:pharmacology*; D051381:Rats
chemical_list: D003470:Culture Media; D010281:Parathyroid Hormone; D010710:Phosphates; D005966:Glucuronidase; D002118:Calcium