Effect of dexamethasone on zinc transport in rat hepatocytes in primary culture.
Incubation of hepatocytes in medium supplemented with 1 microM dexamethasone and 15 or 30 microM ZnCl2 for 24 h resulted in increased intracellular Zn and metallothionein levels. There were a positive correlation between the Zn and metallothionein concentrations. Initial rates of 65Zn influx from balanced salt solutions containing albumin and ZnCl2 to give known free Zn2+ concentrations were measured over 10 min. At 1.6 nM free Zn2+ the influx rate was the same in control and dexamethasone-treated cultures, but at 18 nM free Zn2+ there was an increased rate of influx after dexamethasone treatment. Measurements of 65Zn efflux were quite hard to interpret, because of the existence of at least two intracellular Zn pools, a fast-exchanging and a slow-exchanging pool. The amount of Zn in the fast-exchanging pool appeared to increase as the external free Zn2+ concentration was increased, while the amount in the slow-exchanging pool increased on pre-treatment with Zn and dexamethasone. The fractional efflux of 65Zn from the fast-exchanging pool appeared to increase with the pool size, implying that the rate of Zn efflux increases faster than the concentration of Zn2+ in that pool.
Taylor
J A
JA
Biomedical Sciences Division, King's College London, Strand, UK.
Simons
T J
TJ
D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D014407:Tumor Cells, Cultured; D015032:Zinc / Q000378:metabolism*; D015037:Zinc Radioisotopes
D015037:Zinc Radioisotopes; D003907:Dexamethasone; D015032:Zinc