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Studies on the mechanism of zinc uptake by human fibroblasts
Author(s) -
Ackland M. Leigh,
Danks David M.,
McArdle Harry J.
Publication year - 1988
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041350322
Subject(s) - nigericin , zinc , transferrin , receptor , fibroblast , cell , biophysics , endocytic cycle , chemistry , biochemistry , trypsinization , biology , microbiology and biotechnology , endocytosis , enzyme , membrane , in vitro , trypsin , organic chemistry
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 × 10 7 M −1 . Interestingly, there appears to be a very large number of binding sites, 2 × 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.