644 ADVENTURES IN RADIOISOTOPE RESEARCH 



into the tissue cells, owing to an enhanced metabolism taking place in 

 the cells at this time. Figures 3 and 4 illustrate this type of accelerating 

 effect of adrenahn on the escape of labelled phosphate and labelled iron 

 from the plasma. The rate of escape of sodium ions (Fig. 5), on the 

 contrary, is not affected by the injection of adrenahn. Sodium is es- 

 sentially an extracellular element, although it is incorporated in not 

 inconsiderable amounts into the skeleton and also into the cehs but 

 this process of incorporation is not appreciable during the short experi- 

 mental time of close to 10 min. In this instance, the exchange process 

 takes place almost solely between the plasma and the extracellular space 

 and its rate is therefore not accelerated by the injection of adrenaUn^i^^ 



The investigation by Flexner and co-workers on the rate of escape 

 of labelled iron from the blood plasma was followed by numerous other 

 studies by Lawrence and co-workers^is) and by many other workers. 

 Huff and associates calculate the daily metabolism of plasma iron 

 from the formula^^^^: 



Iron metabolism (mgm/day) = 



0.693 X 24 hr /day X Fe mgm/ml x plasma volume (ml) 



half-life of the disappearing ^^Fe (hr) 



They find that the daily plasma-iron metabolism per kgm of body 

 weight in a healthy person is equal to 0.4 — 0.45 mgm, whereas it is as low- 

 as 0.205 mgm in pathological case such as a refractory anaemia and as 

 high as 3.93 mgm in a case of haemolytic anaemia. 



By determining a fraction of the plasma-^sFe which has accumulated 

 after a definite time in the various organ fractions and in the red blood 

 corpuscles, an explanation is obtained of, among other things, that 

 rather more than one-half of the metabolized iron in a healthy person 

 is used for the synthesis of red blood corpuscles and that this value can 

 fall to one-eighth in refractory anaemia. The metaboHsm of iron in the 

 red blood corpuscles was calculated from the formuWi^). 



^^Fe in the red blood corpuscles 



initial value of ^sFe content in the plasma 

 iron metabolism in the plasma 



THE CONVEYANCE OF IRON FROM THE ORGANS INTO THE PLASMA 



The combining capacity of transferrin for iron is only about one-half 

 utilized in healthy people and also in rabbits, and at first glance it 

 appears remarkable that if indeed a better utilization of this combining 

 capacity can be achieved by parenteral or oral administration the 



