An observational study in Thrombocytopenia, sponsored by National Institutes of Health Clinical Center (CC). Completed at 1 site in United States. Per ClinicalTrials.gov, last updated 2008-03-04.
Sponsored by National Institutes of Health Clinical Center (CC) · Observational
Plasma histidine-rich glycoprotein (HRG) binds to platelets in the presence of zinc (1). This binding is totally blocked by a monoclonal antibody directed against platelet membrane CD36. Therefore, CD36 is assumed to carry the platelet binding site for HRG (2). Because CD36 also has a variety of other ligands, including polyanionic lipids, it is also possible that it contains the binding site for heparin (also polyanionic) and might be involve in the pathogenesis of heparin-induced thrombocytopenia. Demonstrating absent HRG or heparin binding to platelets lacking CD36 would confirm that the binding sites for either or both of these ligands are located on this membrane protein. Because 3% to 11% of healthy Japanese are reported to lack CD36 on their platelets, this population is a practical source of cells for examining the physiologic role(s) for CD36. Therefore, we will recruit blood donors from the Japanese community on the NIH campus. Their platelets will tested for the presence of CD36. Recruitment will be closed after two individuals have been identified whose platelets lack CD36 and who are willing to donate 30 cc of blood on 4 or 5 subsequent occasions for binding studies with radiolabeled HRG and heparin.
Plasma histidine-rich glycoprotein (HRG) binds to platelets in the presence of zinc (1). This binding is totally blocked by a monoclonal antibody directed against platelet membrane CD36. Therefore, CD36 is assumed to carry the platelet binding site for HRG (2). Because CD36 also has a variety of other ligands, including polyanionic lipids, it is also possible that it contains the binding site for heparin (also polyanionic) and might be involved in the pathogenesis of heparin-induced thrombocytopenia. Demonstrating absent HRG or heparin binding to platelets lacking CD36 would confirm that the binding sites for either or both of these ligands are located on this membrane protein. Because 3% to 11% of healthy Japanese are reported to lack CD36 on their platelets, this population is a practical source of cells for examining the physiologic role(s) for CD36. It has also been reported that 2.4% of African Americans and 4% of Taiwanese lack this protein on their platelets. Therefore, we will recruit blood donors from the Japanese, African American, and Taiwanese community on the NIH campus. Their platelets will be tested for the presence of CD36. Recruitment will be closed after two individuals have been identified whose platelets lack CD36 and who are willing to donate 30 cc of blood on 4 or 5 subsequent occasions for binding studies with radiolabeled HRG and heparin.
697 studies on the registry are indexed under Thrombocytopenia; 153 are open to participants now.
This study's enrollment of 150 is above the median of 120 across 183 observational studies indexed under Thrombocytopenia.
Browse Thrombocytopenia studies →National Institutes of Health Clinical Center (CC) is the lead sponsor of 367 studies on the registry; 27 are open to participants now.
Of its 22 completed or terminated interventional studies of FDA-regulated products, 18 (82%) have results posted.
Counted across the registry records on this site, refreshed daily.
Phase I:
Full Japanese, African American, and Taiwanese ancestry
At least 18 years of age.
Willingness and ability to participate in Phase II of the study.
Must be able to provide written informed consent.
Phase II:
Less than 1% CD36 present on platelets, compared with controls.
EXCLUSION CRITERIA:
Phase I:
A history of anemia or thrombocytopenia.
Unwillingness or inability to participate in Phase II of the study.
Phase II:
Discovery of anemia (hemoglobin less than 11.1 g/dL for women, less than 12.7 for men) or thrombocytopenia (less than 162,000/microliter for women, less than 154,000/microliter for men) in the blood counts performed during Phase I.
Subjects will not be excluded because of any medications.
This study is completed, as verified in Feb 2004. You cannot join it, but the record below documents what was studied.
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National Institutes of Health Clinical Center (CC)