Zinc transport into endothelial cells is a facilitated process.
The kinetics of zinc transport were examined by measuring the uptake of 65Zn into cultured endothelial cells. This served as a suitable model for characterizing the transport of zinc across a biological membrane (i.e., the plasma membrane). The transport process was saturable under physiological conditions, which indicates a facilitating transport mechanism. Within the physiological range of zinc concentrations, the maximum zinc transport rate was 27 pmoles zinc/(min x mg protein) and it was half maximal at 4.1 microM zinc. Cadmium competitively inhibited zinc transport (Ki = 6.5 microM), while equimolar concentrations of copper and manganese were ineffectual. The rate of zinc transport was substantially reduced at lower temperatures and in the presence of sulfhydryl blockers (sodium iodoacetate and N-ethylmaleimide). Inhibitors of energy metabolism (2,4-dinitrophenol and sodium azide) failed to disrupt zinc transport. These results demonstrate that zinc transport into endothelial cells is a facilitated process (i.e., it is carrier mediated and energy-independent).
Bobilya
D J
DJ
United States Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, North Dakota 58202-7166.
Briske-Anderson
M
M
Reeves
P G
PG
D019297:2,4-Dinitrophenol; D000818:Animals; D001386:Azides / Q000494:pharmacology; D001692:Biological Transport / Q000502:physiology; D002104:Cadmium / Q000493:pharmacokinetics / Q000494:pharmacology; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D002478:Cells, Cultured; D003300:Copper / Q000493:pharmacokinetics / Q000494:pharmacology; D004140:Dinitrophenols / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D005033:Ethylmaleimide / Q000494:pharmacology; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D008345:Manganese / Q000493:pharmacokinetics / Q000494:pharmacology; D019810:Sodium Azide; D012969:Sodium Fluoride / Q000494:pharmacology; D013696:Temperature; D015032:Zinc / Q000493:pharmacokinetics*; D015037:Zinc Radioisotopes
D001386:Azides; D004140:Dinitrophenols; D007461:Iodoacetates; D015037:Zinc Radioisotopes; D002104:Cadmium; D008345:Manganese; D003300:Copper; D012969:Sodium Fluoride; D019810:Sodium Azide; D015032:Zinc; D005033:Ethylmaleimide; D019297:2,4-Dinitrophenol; D019807:Iodoacetic Acid