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DIFFERENTIAL REGULATION OF GROWTH PLATE CHONDROCYTES BY 1 ,25-(OH)2D3 AND 24R,25-(OH)2D3 INVOLVES CELL-MATURATION-SPECIFIC MEMBRANE-RECEPTOR-ACTIVATED PHOSPHOLIPID METABOLISM
B.D. Boyan1,*,2,3,
V.L. Sylvia1,
D.D. Dean1,
F. Del Toro1,4 and
Z. Schwartz1,2,5
1 Departments of Orthopaedics,
2 Periodontics,
3 Biochemistry, and
4 Orthodontics, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, MS-7774, San Antonio, TX 78229-3900; and
5 Department of Periodontics, Hebrew University Hadassah Faculty of Dental Medicine, Jerusalem, Israel;
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Figure 1. Neutral metalloproteinase (MMP) and collagenase content of growth plate cartilage from normal and vitamin D/phosphate-deficient (-VDP) rats. At the animals' death, the proximal tibial growth plate cartilage was removed, and neutral MMP and collagenase were extracted and then assayed on aggrecan and type 1 collagen substrates. All values are the mean ± SEM in enzyme units/gram wet weight tissue for n  7 samples. *P < 0.05, normal vs. –VDP.
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Figure 3. Effect of inhibiting PLC on protein kinase C (PKC) activity in resting zone (RC) and growth zone (GC) chondrocytes. Confluent, fourth-passage RC cells were treated with 10-7 M 24R,25-(OH)2D3 for 90 min (left panel), and GC cells were treated for 9 min with 10-8 M 1 ,25-(OH)2D3 (right panel) in the presence or absence of the phospholipase C inhibitor U73122 (10 µM). At harvest, PKC specific activity in the cell layer was determined. Data represent the mean ± SEM of 6 cultures from one of two experiments yielding comparable results. *P < 0.05, treatment vs. control; •p < 0.05, U73122 vs. no U73122.
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Figure 4. Effect of inhibiting PLD on protein kinase C (PKC) activity in resting zone (RC) and growth zone (GC) chondrocytes. Confluent, fourth-passage RC cells were treated with 10-7 M 24R,25-(OH)2D3 for 90 min (left panel), and GC cells were treated for 9 min with 10-8 M 1,25-(OH)2D3 (right panel) in the presence or absence of the phospholipase D inhibitor wortmannin (10 µM). At harvest, PKC specific activity in the cell layer was determined. Data represent the mean ± SEM of 6 cultures from one of two experiments yielding comparable results. *P < 0.05, treatment vs. control; •p < 0.05, wortmannin vs. no wortmannin.
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Figure 5. Effect of activating PLA2 on protein kinase C (PKC) activity in resting zone (RC) and growth zone (GC) chondrocytes. Confluent, fourth-passage RC cells were treated with 10-7 M 24,25-(OH)2D3 for 90 min (left panel), and GC cells were treated for 9 min with 10-8 M 1,25-(OH)2D3 (right panel) in the presence or absence of the phospholipase A2 activator melittin (0.3 µg/mL). At harvest, PKC specific activity in the cell layer was determined. Data represent the mean ± SEM of 6 cultures from one of two experiments yielding comparable results. *P < 0.05, treatment vs. control; •p < 0.05, melittin vs. no melittin.
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Figure 6. Mechanism of action of vitamin D3 metabolites. Proposed pathways of action of 1,25-(OH)2D3 in growth zone chondrocytes (GC) and 24,25-(OH)2D3 in resting zone chondrocytes (RC). Phospholipase C (PLC), Phospholipase A2 (PLA2), arachidonic acid (AA), cyclooxygenase-1 (Cox-1), PGE2 EP receptor (EP), phospholipase D (PLD), protein kinase C (PKC), protein kinase A (PKA).
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Critical Reviews in Oral Biology & Medicine, Vol. 13, No. 2,
143-154 (2002)
DOI: 10.1177/154411130201300205
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