Interactions between the histidine stimulation of cadmium and zinc influx into human erythrocytes.
1. Histidine (2-40 mM) stimulated cadmium uptake into human erythrocytes incubated in the presence of 1% bovine serum albumin to ensure that the free, ionic cadmium concentration was low. 2. The histidine-stimulated cadmium uptake correlated with the calculated concentration of the cadmium-bis-histidine complex rather than the cadmium-mono-histidine complex or free ionic cadmium. 3. The histidine stimulation of cadmium uptake was saturable and stereospecific. D-Histidine (10 mM) had no effect. 4. Cadmium and zinc were both able to inhibit 65Zn2+ uptake into erythrocytes incubated in the presence of 40 mM L-histidine. The relationships between the percentage inhibition of 65Zn2+ uptake and the calculated concentrations of cadmium-bis-histidine and zinc-bis-histidine were very similar, which suggests that the metal histidine complexes compete for a common transport mechanism. 5. Pretreatment of the erythrocytes with N-ethylmaleimide using a protocol which is known to inhibit the system y+ amino acid transport mechanism had no effect on the histidine stimulation of metal transport.
Horn
N M
NM
Department of Physiology and Pharmacology, University of Southampton, UK. NMH@soton.ac.uk
Thomas
A L
AL
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002104:Cadmium / Q000097:blood*; D002417:Cattle; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D006639:Histidine / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D012710:Serum Albumin, Bovine; D015032:Zinc / Q000097:blood*; D015037:Zinc Radioisotopes
D015037:Zinc Radioisotopes; D002104:Cadmium; D012710:Serum Albumin, Bovine; D006639:Histidine; D015032:Zinc; D005033:Ethylmaleimide