Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/1996
Publication Date: N/A
Interpretive Summary: While much of the copper found in human plasma is irreversibly bound into large proteins, a small amount of plasma copper is loosely bound. This loosely bound copper is the initial form of copper absorbed from the gut. Tightly or loosely bound copper may be separated from each other; however, these separation procedures require several hours during which changes in the copper distribution may occur. We have developed a procedure to separate the loosely bound copper in less than one hour which preserves the distribution of copper between the irreversible and loosely bound forms of copper. We have used the procedure to measure the loosely bound copper in a variety of animals and ten men. In the future and hope to used this procedure to help define human copper requirements.
Technical Abstract: Direct reacting copper (DR Cu) is defined as Cu2+ and other forms of copper that readily exchange with Cu2+ in blood plasma. An analytical method was developed for 1) quantification of DR Cu by stable isotope dilution and 2) determination of 65Cu enrichment of DR Cu in plasma samples from in vivo tracer studies. The method involved addition of enriched 65Cu to plasma, extraction with sodium diethyldithiocarbamate (NaDDC) in mineral oil, and analysis by inductively coupled plasma mass spectrometry. Optimum NaDDC concentration for the extraction was 0.16 mM. Direct reacting Cu (means +/- SD) varied from 3.4 +/- 0.5% of whole plasma Cu in dairy cows (n=7) and 3.4 +/- 0.3% in healthy men (n=10) to 16.6 +/- 3.7% in dogs (n=3). Following intravenous infusion of enriched 65Cu into two healthy men, biological half- lives of 8.7 and 12.3 min were determined for DR Cu.