TRANSPORT MECHANISMS FOR IRON AND OTHER TRANSITION-METALS IN RAT AND RABBIT ERYTHROID-CELLS

1. Earlier studies have shown that Fe2+ transport into erythroid cells is inhibited by several transition metals (Mn2+, Zn2+ Co2+, Ni2+) and that Fe2+ transport can occur by two saturable mechanisms, one of hig h affinity and the other of low affinity. Also, the transport of Zn2and Cd2+ into erythroid cells is stimulated by NaHCO3 and NaSCN. The a im of the present investigation was to determine whether all of these transition metals can be transported by the processes described for Fe 2+, Zn2+ and Cd2+ and to determine the properties of the transport pro cesses. 2. Rabbit reticulocytes and mature erythrocytes and reticulocy tes from homozygous and heterozygous Belgrade rats were incubated with radiolabelled samples of the metals under conditions known to be opti mal for high-and low-affinity Fe2+ transport and for the processes med iated by NaHCO3 and NaSCN. 3. All of the metals were transported by th e high-and low-affinity Fe2+ transport processes and could compete wit h each other for transport. The K-m and V-max values and the effects o f incubation temperature and metabolic inhibitors were similar for all the metals. NaHCO3 and NaSCN increased the uptake of Zn2+ and Cd2+ bu t not the other metals. 4. The uptake of all of the metals by the high -affinity process was much lower in reticulocytes from homozygous Belg rade rats than in those from heterozygous animals, but there was no di fference with respect to low-affinity transport.5. It is concluded tha t the high-and low-affinity 'iron' transport mechanisms can also trans port several other transition metals and should therefore be considere d as general transition metal carriers.