Disposition of Bismuth in the Rat. I. Red Blood Cell and Plasma Protein Binding

The plasma protein and red blood cell binding profile of bismuth was investigated as a function of bismuth concentration. The binding of bismuth to human serum albumin, bovine serum albumin, and human plasma was also evaluated by ultrafiltration and the data analyzed by nonlinear regression techniques. The binding of bismuth to plasma proteins was nonlinear and decreased as a function of incubation concentration and appeared to be limited by the number of ionized 1-cysteine residues available for binding. In the concentration range studied, bismuth was associated primarily with the red blood cell fraction of whole blood obtained from male Sprague Dawley rats. The data indicated that binding to proteins was of moderate affinity, and in whole blood it was present primarily in the red blood cell compartment.