626 



ADVENTURES IN RADIOISOTOPE RESEARCH 



ved Tn!Zrrr Z ' P^-^P^^-t-d Win washed with 1 N HCl and dissol- 

 ^ed m ether The ether was evaporated and the hemin combusted with snlfurie 

 acid and hydrogen peroxyde. The determination of iron was carried out bv a 

 colorimetric method using the sulfosahcyhc acid complex ^ 



onnt" fT""^ °!"J^^ V ^''*'°'' '^^' ^'"^ ^°" colorimetric determination of the iron 

 ZlTol" Tb ^"°' -on chloride was added brmging its iron content up 



to 500 /^g. The iron was precipitated as FeS and filtered through a perforated 

 alummium dish covered with filter paper as described by Aonek et a J The alu- 

 minium dish was then placed under the window of a Geiger counter. An aliquot 

 of the olution which was injected was treated in the same way. The data obtaled 

 permitted to calculate the relative specific activity of the iron fraction (activitv 

 per -g- -on m arbitrary units) and also the absolute specific activity (percentage 

 of injected ^spe present in 1 mgm of iron). ^«iiiage 



Inour experiments on the iron turnover of the plasma 5-10 ^gm of iron having 

 an activity of about 2 ^Curie were injected into the ear vein of a rabbit. Aftef 

 the lapse of about 1 h a few ml of the plasma of this rabbit, which now contained 

 all -Fe present m the plasma as /5,-globuUn, was injected into the jugular vein 



of thf '^Vwf \ ' "'^'""^ ^'°°^^ ^"^P^^^ ™ ^^^- f-- t^^ --tic vein 

 of hs rabbit the heparmized blood centrifuged, the plasma combusted as descri- 

 bed above, 500 /.gm carrier iron added and the iron precipitated as sulphide as 

 described above. 2 3 kgm rabbits were applied in these Txperiments, in whi" 

 the effect of irradiation on the formation of labelled hemoglobin and labelled 

 nemm o± the bone marrow was investigated. 



RESULTS 



a) Cytochrome b 



The data obtained for the ratio of the specific activities of cytochrome 

 biron (Strittmatter(2^)) and also of microsome ferritin iron of irradiate 

 and control guinea-pigs are listed in Table 1. Out of 13 ratios listed in 

 iable 1, one is as low as 0.77, but even this ratio is by about 250o/o higher 

 than that obtained for hemoglobin iron, which was found to be 3 

 corresponding to a depression of ^^Fe incorporation into hemoglobin 

 in the irradiated guinea-pig to V3 of that into the hemoglobin of controls 

 Not only does exposure of guinea-pigs to large doses of Roentgen rays 

 not diminish the rate of incorporation of the ^^Fe into cytochrome b but 

 as seen in Table 1 promotes it. The increased incorporation of ^^Fe does 

 however, not or not mainly indicate an increased rate of formation of 

 cytochrome b. It is, at least to a large extent, due to the change in sen- 

 sitivity of the radioactive indicator. A larger part of the plasma iron takes 

 Its way into the bone marrow and is applied to hemoglobin synthesis 

 a minor part into the liver and other organs. The labelled iron atoms 

 which leave the plasma are replaced by inactive ones coming from the 

 organ depots and to a minor extent from the intestine. Irradiation upsets 

 distribution. Incorporation into hemoglobin is strongly reduced which 

 results in an increased life-time of^m in the plasma which in turn leads 



