Studies on the mechanism of zinc uptake by human fibroblasts

✍ Scribed by M. Leigh Ackland; David M. Danks; Harry J. McArdle

• Publisher: John Wiley and Sons
• Year: 1988
• Tongue: English
• Weight: 584 KB
• Volume: 135
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041350322

✦ Synopsis

The mechanisms of zinc uptake from a complete culture medium by human fibroblasts have been studied. The metal is accumulated in a biphasic pattern; an initial rapid phase followed by a slower linear phase. We suggest that the former represents binding to carriers or receptors on the cell surface followed by uptake to within the cell, or at least to a compartment inaccessible to proteolytic digestion. The uptake correlates well with estimates of the zinc requirement of a growing fibroblast. The process of uptake is saturable, with an apparent association constant of 1.1 X 10(7) M-1. Interestingly, there appears to be a very large number of binding sites, 2 X 10(7) per cell. No explanation for this observation is immediately apparent. The mechanism of uptake is not dependent on metabolic energy, or at least on ATP levels within the cell, but N-ethyl maleimide does block uptake in a dose-dependent manner. Weak bases and ionophores, apart from nigericin, do not affect uptake. The results suggest that zinc is not taken up by a receptor-mediated endocytic pathway as has been described for transferrin and iron.