77
rate were not practicable under the conditions of this study.
Nevertheless it was possible to obtain an estimate of the
relative turnover rate of zinc in some of the fish tissues
sampled for this study.
The zinc turnover rate of a tissue
can be considered to be a function of
and
(2)
its exchange capacity.
(1)
its rate of uptake
The relative values of zinc-65
taken up from solution by various tissues of catfish in a given
time
(Joyner,
1961) were used as an estimate of the rate of
uptake of similar tissues in goatfish.
The zine turnover rate
(T) was considered a function of the rate of uptake
(u)
and the
exchange capacity (x), giving the relationship T = f(u,x).
estimate of T was
obtained from u-x.
The relative values of
T for different tissues are shown in Table 9.
mates,
From these esti-
it would appear that the highest turnover rate in the
tissues for which values are given is found in the G.
followed by gill filament,
order.
An
liver,
I.
tract,
muscle and bone in descending
It is unfortunate that an estimate of the uptake of zinc
in the eye was not available from the catfish data.
Consequently
no estimate of zinc turnover rate was possible for this tissue.
The high turnover values for G.
I.
tract and liver would
be expected from the intenge metabolic activity associated with
these tissues and the fact that zinc enzymes are associated with
much of this activity.
The high value in gill filament is