title: Uptake of lead by human red blood cells and intracellular distribution.
abstract: Lead added to plasma was rapidly incorporated into suspended human red blood cells at 37 degrees C. The rate of lead uptake into the cells reached a maximum of 35 micrograms (0.17 mumole)/10(10) cells/h. The rate of lead uptake with resealed ghosts was comparable to that of intact cells. These findings indicate that the transport of lead across the erythrocyte membrane is, energy-independent, carrier-mediated passive transport, which confirms the conclusion of Simons. On the other hand, little release of incorporated lead from the cells in lead-free plasma was observed. Some 98% of intracellular lead was in cytoplasm, mostly in protein-bound form, and only 2% was in the membrane fraction. When red blood cells were incubated in plasma containing lead at about 10 mg/dl concentration for 24 hours at 37 degrees C, no progressive accumulation of lead and protein in the membrane fraction was observed. Thus, lead-protein complexes in cytosol are unlikely to associate with membranes. Human haemoglobin had forty-five binding sites for lead with the dissociation constant of 0.5 x 10(-6) M. The binding of lead to oxyhaemoglobin did not show any effect on the iron atom in the heme.
authors: Department of Research, Chubu Rosai Hospital, Nagoya, Japan.
authors: E
authors: E
authors: Sugawara
authors: K
authors: K
authors: Nakamura
authors: A
authors: A
authors: Fukumura
authors: Y
authors: Y
authors: Seki
mesh_terms: D001665:Binding Sites; D001692:Biological Transport; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D007854:Lead / Q000097:blood*
chemical_list: D006454:Hemoglobins; D007854:Lead; C029891:lead chloride