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is related to the relative strengths of bonds formed between
zinc ions and the carriers with which they are associated in
the body fluids and between zinc ions and the binding sites
on the tissue components.
Table 9 summarizes the rank relationships of the data
presented in Table 5,
From these ranks it is possible to
infer the relative zine binding and exchange capacities of
the different tissues.
The ranks of the total zinc levels of
the various tissues listed in the table suggest their relative
zine binding capacity,
since the supply from the stable zinc
dissolved in sea water is virtually constant.
The ranks of
the levels of zinc-65 are indicative of the relative zinc
exchange capacities of the tissues,
sgince the presence of
Zine-65 in a given tissue implies exchange with stable zinc
ions ordinarily present.
A useful parameter for considering the physiological
role of metals is the turnover rate of the metal in the biological system under consideration.
The length of time which
the metal may be expected to reside in the system,
biological half-life,
measured as
is a function of the turnover rate.
The
turnover rates for various elements in biological systems are
commonly measured under laboratory conditions using radioactive
tagging methods.
Unfortunately,
such determinations of turnover