Fast uptake kinetics in vitro of 51Cr (VI) by red blood cells of man and rat.

Fast transport kinetics of 51Cr (VI) into red blood cells (RBCs) in vitro were studied. No significant species differences were found between RBCs of man and rat. The uptake of 51Cr (VI) by RBCs in whole blood was composed of two different first order processes of different velocities (apparent t 1/2 of 22.7 s and 10.4 min for man and 6.9 s and 10.1 min for rat, respectively). However, even after longer time periods a fixed portion of approximately 15% of the administered dose remained in the plasma and did not penetrate into RBCs Over the entire concentration range studied (10 microM-50 mM), the fast initial uptake followed Michaelis-Menten kinetics. The maximal capacity of this Cr(VI) transport into RBCs of man and rat was 3.1 X 10(8) CrO4(2-) ions X cell-1 X min-1 and 2.5 X 10(8) CrO4(-2) ions X cell-1 X min-1, respectively. It is likely that Cr(VI) is transported into RBCs via a physiological anion carrier ("band-3-protein").