Studies with Fe-59 on the transport of serum iron in birds

Abstract

In our previous works (8, 9, 10) we have shovved that in lay- ing birds the serum iron increases greatly thus surpassing the valúes of the total iron-binding capacity (TIBC), deter- minated by the Ramsay's method (11).

Others works done with Fe59 in birds (2, 5, 6) do not con­ cern the transport mechanism.

We have studied the species : Gallus domesticus (3 females and 1 male) and .4»us platyrhynca, var. Kaki-Campbell (3 females).

The radioactive iron had an activity of 55 p. c. in 9.2 p g of iron element, as citrate, dissolved in 2.3 cc of isotonic solution.

For the studies in vitro the desired quantity of Fe59 has been added to the serum in a test tube. For the studies in vivo the Fe39 has been incubated with serum of the same specie for 15 minutes and afterwards injected in the vein.

Serum with Fe39 was subjected to paper-electrophoresis, and the paper strips were autoradiographied with an X-Rayfilm. In some strips the radioactivity has been measured with a Geiger counter.

Serum iron and TIBC have been determined following Ramsay's methods (12, 11).

The radioactivity in ducks is found exclusively upon the /?-globulins (Fig. Ib and 1c; Fig. 3). In hens and chicken in vitro the Fe39 is seen in all the globulins, but very specially in the /3 fraction (F'ig. 2a, 2b ; Fig. 4 and Fig. 5). In the only case that we were able to find radioactivity in the serum after Fe59 injection (Hen n.° III : Fig. 2c and Fig. 6) the radioac­

tivity was found upon the /?-globulins.
Studies done in this laboratory shown that a part of the

circulating iron is carried off by. adding magnesium carbonate to the serum. This iron, as we have seen, is in ducks exclusi­ vely bound at the /3-globulins. In hens, it is also bound in its great part to these globulins, as in vitro the iron can also be bound to other globulins.

A part of these iron, precisely the one which is carried off by the magnesium carbonate, must necesarily be bound to the/?-globulins in a more labile form.

We have also becn able to notice from our experimcnts in vivo that the turnover of the plasma iron in birds during the lajdng period is especially active.