RADIOIODINE 



213 



RADIOPHOSPHORUS 



rally attracted much attention. Hertz, 

 S., Roberts, A. and Evans, R.D.,Proc. 

 Soc. Exper. Biol. Med., 1938, 38, 510- 

 513 first demonstrated the rapid uptake 

 of radioiodine in the thyroid gland. 

 Increase of the radiosalt is even more 

 rapid in hyperplastic thyroids. Nu- 

 merous studies on thj'roids of humans 

 have been reported by Hamilton, J. G. 

 and Soley, M. H., Am. J. Physiol., 1939, 

 127, 557-572 and ibid, 1940, 131, 135- 

 143. Much of this work was done on 

 the living glands by measuring the 

 gamma radiation from the neck region 

 over the thyroids by a Geiger-Miiiler 

 coimter. These same workers, with the 

 cooperation of Eichoru, K. B., Univ. 

 Calif. Publ. Pharmacology, 1940, 1, 

 339-367 demonstrated, by means of the 

 technique of autoradiography, that radio- 

 iodine is deposited in the colloid of 

 normal and hyperplastic thj^roids. The 

 storage is markedly lower in the colloid 

 of nontoxic goiter, and almost no radio- 

 iodine enters cancerous thyroid tissue. 

 Mention has already been made of the 

 work of Gorbman and Evans on deter- 

 mination by autoradiography of time of 

 first storage of radioiodine in the thy- 

 roids of embryonic frogs. 

 Radiciron (Fe^s) half life 47 days. Yield 

 very low. (Fe^^) with a half life of 4 

 yrs. has not been much used as yet in 

 biological problems. What follows re- 

 lates to Fe^^ 



Whipple and his associates have 

 availed themselves of radioiron to show 

 that iron metabolism is controlled by 

 the rate of absorption of the iron salts 

 from the intestine and not by the rate 

 of elimination of the iron already in the 

 tissues. A higher proportion of ab- 

 sorbed iron goes into the formation of 

 hemoglobin in anemic animals than 

 in normal ones. The rate of absorp- 

 tion from the intestine seems to be 

 controlled bj^ the iron content of the 

 tissues, especially of the intestinal 

 mucosa, and not by degree of anemia 

 per se. See numerous papers by Whip- 

 ple, G. H., Bale, W. F., Lawrence, E. 0., 

 Hahn, P. F. et al., chieflv in the J. 

 Exper. Med., 1938-1941, much of which 

 is confirmed by Austoni, M. E. and 

 Greenberg, D. M., J. Biol. Chem., 

 1940, 134, 27-41 who also demonstrate 

 that the muscles serve as an important 

 storehouse for iron in anemia. 



Use of erythrocytes "tagged" with 

 radioactive iron opens up a new approach 

 to many baffling problems in hematology. 

 One recent investigation employing 

 such labeled red cells is that of Chapin, 

 M. A. and Ross, J. F., Am. J. Physiol., 

 1942. 137, 447-155 who checked the 

 values for true red cell volume using 

 "tagged" erythrocytes in comparison 



with results from dye dilution, protein 

 dilution, and the hematocrit. The 

 technique of measuring the activity of 

 such red cells is described by Ross, J. 

 F. and Chapin, M. A., Rev. Sci. Instr., 

 1942, 13, 77-80. Erythrocytes can also 

 be labeled with radiophosphorous. 



Radiomanganese (Mn^<) half life 310 days. 

 Not much use has been made of this 

 isotope to date but Greenberg, D. M. 

 and Campbell, W. W., Proc. Nat. Acad. 

 Sci., 1940, 26, 448-452 have observed 

 that 90% of ingested radiomanganese 

 is eliminated in the feces within 75 hrs. 

 The highest retention is in the liver, 

 bones, and muscles. 



Radionitrogen (N^s) half life 9.93 min. 

 Short useful life limits study to experi- 

 mental procedures that are completed 

 within approximately 1 hr. Ruben, S., 

 Hassid, W. Z. and Kamen, M. D., 

 Science, 1940, 91, 578 have found that 

 it enters into the complex compounds 

 within barley plants which live in air 

 containing it. Whether this represents 

 nitrogen fixation by a non-leguminous 

 plant, or a simple exchange between 

 the radionitrogen and ordinary nitro- 

 gen within the plant, is not established 

 as yet. 



Radiophosphorus (P^^) j^^jf jjfg 14 3 days. 

 Employed more extensively than any 

 other isotope, radiophosphorus is rather 

 easy to prepare and its useful life is 

 long enough to permit most experi- 

 mental procedures, and short enough 

 to allow ready detection with the Geigcr- 

 Miiller counter or photographic plate of 

 radiation from its decay. Since no 

 gamma rays arc given off during its 

 decay radiophosphorus can not be de- 

 tected in the intact organism, except 

 in the skin. Also encoui'aging its use 

 is the fact that phosphorus plaj's such 

 an extensive role in the compounds 

 found in living organisms. In deciding 

 whether to employ radiophosphorus it 

 IS helpful to bear in mind the kinds of 

 work in which it has already proved 

 useful. 



Chiewitz, O. and Hevesy, G. (Nature, 

 1935, 136, 754) were the first to use 

 artificially produced radioactive isotopes 

 in biological research. Initial studies 

 were devoted to investigation of metabo- 

 lism of P^2 in rats. Absorption and 

 excretion of P'^ in experimental animals 

 and humans have been studied by Hevesy 

 and coworkers, Lawrence and associates, 

 and Greenberg and Cohn. At least 

 70% of ingested P^^ (as inorganic phos- 

 pliates) is absorbed from intestine when 

 fed to a fasting subject. The balance 

 is excreted in feces. Glucose and 

 neutral fat enhance absorption. In- 

 travenous disodium phosphate con- 

 taining tracer quantities of P'^ in the 



