Whole blood or plasma from male human volunteers or pooled from male Sprague-Dawley rats was incubated with varying amounts of 3H-2,3,7,8-tetrachlorodibenzo-p-dioxin (3H-TCDD). Blood was separated into cellular, protein and lipoprotein fractions by centrifugation. The distribution of 3H-TCDD between lipoproteins and plasma proteins was independent of 3H-TCDD concentration in the range of 65 fmol-1 nmol/ml plasma. The distribution of 3H-TCDD between the various lipoprotein fractions depended only on their relative content of total cholesterol plus triglycerides. The partitioning of 3H- TCDD between lipoproteins and plasma proteins was inversely proportional, whereas the distribution between the cellular fraction and the lipoproteins was directly proportional to the total plasma cholesterol plus triglyceride content. As a consequence of species differences in blood composition, the major part of 3H-TCDD-associated radioactivity was recovered from lipoproteins in human blood but from erythrocytes in rat blood. A mathematical description of the distribution of TCDD between blood components is presented.
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