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Articles |
Departments of
1
Medicine and
2
Microbiology and Immunology, University of Louisville, Louisville, KY 40292.
3
Special Hematology Laboratory, Veterans Affairs Medical
Center, Louisville, KY 40206.
4
Institute of Biomedicine, Department of Anatomy,
University of Turku, Turku, Finland.
a Address correspondence to this author at: Veterans Affairs Medical Center, 800 Zorn Ave., Louisville, KY 40206. Fax 502-894-6155; e-mail lungyam{at}pol.net
Background: Tartrate-resistant acid phosphatase (TRAP; EC 3.1.3.2) is a product of osteoclasts and a biochemical marker of bone resorption rate. However, erythrocytes and platelets contribute to total TRAP activity in serum, reducing the specificity of direct biochemical assays in serum. Osteoclast TRAP is also known as type-5 TRAP and is antigenically unique. Immunoassays are sought to improve the specificity and sensitivity of TRAP as a bone marker.
Methods: We developed two colorimetric microplate assays for type-5 TRAP: an enzyme capture immunoassay to measure antibody-bound enzymatic activity, and a two-site immunoassay to measure bound enzyme protein. Both use the same monoclonal antibody (14G6) to capture type-5 TRAP, which permits determination of specific activity of serum TRAP in health and disease.
Results: Both TRAP assays were linear from one-tenth to fivefold the mean value in 18 healthy subjects. In these subjects, the mean (SD) TRAP activity was 3.2 (0.54) U/L for the enzyme capture assay and 37 (13) µg/L for the two-site assay. Mean TRAP activity was not significantly increased in 64 patients with endstage renal disease requiring hemodialysis (HD) or 99 unselected patients with rheumatic diseases. By contrast, TRAP protein was increased in both the HD and rheumatic disease groups. The specific activity of TRAP in the 17 of 64 HD sera that had increased TRAP activity (0.088 U/µg) was similar to that in healthy subjects (0.091 U/µg). By contrast, the specific activity of TRAP in the 31 of 99 rheumatic sera with increased TRAP protein (0.035 U/µg) was significantly decreased.
Conclusions: Wide sample distributions for TRAP activity in HD patients and TRAP protein in rheumatic disease patients suggest the presence of subpopulations of HD patients with increased TRAP activity and of rheumatic patients with increased TRAP protein. Each assay for TRAP activity and protein may have its own biological significance and clinical applications in specific groups of patients.
The following articles in journals at HighWire Press have cited this article:
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  A. J. Janckila, R. N. Parthasarathy, L. K. Parthasarathy, R. S. Seelan, Y.-C. Hsueh, J. Rissanen, S. L. Alatalo, J. M. Halleen, and L. T. Yam Properties and expression of human tartrate-resistant acid phosphatase isoform 5a by monocyte-derived cells J. Leukoc. Biol., February 1, 2005; 77(2): 209 - 218. [Abstract] [Full Text] [PDF]
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 T.-Y. Chao, J.-C. Yu, C.-H. Ku, M. M. Chen, S.-H. Lee, A. J. Janckila, and L. T. Yam Tartrate-Resistant Acid Phosphatase 5b is a Useful Serum Marker for Extensive Bone Metastasis in Breast Cancer Patients Clin. Cancer Res., January 15, 2005; 11(2): 544 - 550. [Abstract] [Full Text] [PDF]
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 A. J. Janckila, W.-K. Yang, R.-J. Lin, C.-J. Tseng, H.-Y. Chang, J.-M. Chang, and L. T. Yam Flow Cytoenzymology of Intracellular Tartrate-resistant Acid Phosphatase J. Histochem. Cytochem., September 1, 2003; 51(9): 1131 - 1135. [Abstract] [Full Text] [PDF]
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 J. M. Halleen, S. L. Alatalo, A. J. Janckila, H. W. Woitge, M. J. Seibel, and H. K. Vaananen Serum Tartrate-resistant Acid Phosphatase 5b Is a Specific and Sensitive Marker of Bone Resorption Clin. Chem., March 1, 2001; 47(3): 597 - 600. [Full Text] [PDF]
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A. J. Janckila, K. Takahashi, S. Z. Sun, and L. T. Yam Tartrate-resistant Acid Phosphatase Isoform 5b as Serum Marker for Osteoclastic Activity Clin. Chem., January 1, 2001; 47(1): 74 - 80. [Abstract] [Full Text] [PDF]
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