PARATHYROID-HORMONE REGULATION OF MATRIX DEGRADING ENZYMES IN RAT OSTEOBLASTIC OSTEOSARCOMA 17 2.8 CELLS/

The present study was designed to further understand the role of PTH o n the secretion of the neutral metallo-proteinases, collagenase and ge latinase, from the rat osteosarcoma clonal cell line, ROS 17/2.8. Semi confluent cells were treated with bovine parathyroid hormone, b-PTH-(1 -34) at 100 nM-0.01 nM for 24-96 hours and pooled, concentrated media were analyzed by functional assay for collagenase (H-3-methyl collagen ) and gelatinase (H-3-methyl gelatin). Collagenase activity significan tly decreased (P < 0.01) in the PTH conditioned media in a dose-depend ent manner before (98-64%) and after (91-39%) reduction and alkylation . SDS-PAGE and fluorography apparently showed the most degradation to alpha(A) chains in collagen with controls, whereas this substrate rema ined intact with PTH (100 nM). PTH (100 nM) media also showed neutral gelatinase activity approximately 2% compared to control before and af ter reduction and alkylation (P < 0.01). Significant amounts of an inh ibitor to collagenase and gelatinase might have been secreted at 1 nM and 0.01 nM PTH, since collagenase and gelatinase activities were grea ter after reduction and alkylation. Reduction and alkylation likely de stroyed these significant amounts of inhibitor. Polymorphonuclear leuk ocyte collagenase activity was also inhibited 80% by PTH conditioned m edia, but not by control. However, upon reduction and alkylation which destroyed inhibitor, the PTH treated media showed only a 14% inhibiti on against polymorphonuclear leukocyte collagenase (P < 0.01). PTH app eared to downregulate neutral metalloproteinase activities through its effects on an inhibitor. This downregulation may represent a specific phenotypic response to PTH in ROS 17/2.8 cells.