RADIOCALCIUM 



212 



RADIOIODINE 



Pecher also predicted that strontium is 

 handled in the body in the same fashion 

 as shown in his experiments. Long half 

 life makes this element rather difficult 

 to work with. 



Radiocarbon (C") half life 21 min._ Short 

 life makes use difficult in many investi- 

 gations. In spite of this handicap, S. 

 Ruben, M. D. Kamen and their co- 

 workers have used radiocarbon to study 

 CO2 metabolism and photosynthesis in 

 a wide variety of lower animals and 

 plants. Their findings on the nature of 

 photosynthesis, at variance with the long 

 accepted view, afford a nice illustration 

 of the manner in which well planned 

 experiments with the radioisotopes can 

 support or dispel classical assumptions. 

 They showed, for instance, that chloro- 

 phyll containing plants can assimilate 

 radiocarbon dioxide in the absence of 

 light and convert it to a carboxylicacid 

 radical attached to a particle of high 

 (approximately 1090) molecular weight. 

 The process is limited in the absence of 

 light, but in the presence of light as- 

 similation continues with a photosyn- 

 thetic reduction of the carboxylic acid 

 radical to an alcohol group with the 

 liberation of oxygen . This newly formed 

 alcohol radical accepts CO2 in another 

 non-photosynthetic reaction. Succes- 

 sive alternate photosynthetic and non- 

 photosynthetic reductions lead to the 

 building of longer carbon chain radicals 

 on the large enzyme molecule. Pre- 

 sumably these chains eventually split 

 off as simple sugars, etc. See Ruben 

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

 (J. Am. Chem. Soc, 1939, 61, 661 

 1940, 62, 34-13), Ruben, S., Kamen, M 

 D., Perry, L. H., ibid, 1940, 62, 3450 

 Ruben, S. and Kamen, M. D., ibid, p 

 3451. Kamen, M. D. and Ruben, S. 

 J. Appl. Physics, 1941, 12, 310A suggest 

 the possibility of i?i vivo synthesis of 

 sugars, acetic acid, etc. from radiocarbon 

 as a means of obtaining radioactive sub- 

 stances that are too complex to be 

 synthesized in the laboratory in the 

 time available during the useful life of 

 radiocarbon. 



Radiocarbon (C^^) half life estimated to be 

 over 1000 years. Very small quantities 

 are produced but specific activity is 

 high. It may be useful for stud}'- of 

 some biological problems. 



Radiochlorine (Cps) half life 37 min. Used 

 chiefly to investigate rate of chloride ion 

 penetration into various tissues (Man- 

 ery, J. F. and Haege, L. F., Am. J. 

 Physiol., 1941, 134, 83-93). The per- 

 meability of human erythrocytes to 

 radiochloride ion lias been determined 

 and compared with permeability toother 

 non-radioactive ions by Smith, P. K., 

 Eisenmann, A. J. and Winkler, A. W., 



J. Biol. Chem., 1941, 141, 555-561. A 

 complete exchange between radio - 

 chloride ions of serum and erythrocytes 

 was found within less than 10 min. 



Radiocobalt (Co") half life— 270 days. 

 Little work has been done with this 

 isotope. Copp, D. H. and Greenberg, 

 D. M., Proc. Nat. Acad. Sci., 1941, 27, 

 153-157 report on the distribution of 

 minute doses. The bulk of ingested 

 radiocobalt is rapidly excreted. Less 

 than 5% is retained after 4 days. This 

 fraction is found chiefly in pancreas, 

 kidney, spleen, and liver. The inter- 

 esting question is raised of a possible 

 relation between cobalt retention in the 

 pancreas and the association of cobalt 

 with insulin. 



Radiocopper (Cu^'») half life 13 hrs. Dis- 

 tribution in blood serum and red cells 

 has been briefly reported by Yoshikawa, 

 H., Hahn, P. F. and Bale, W. F., Proc. 

 Soc. Exper. Biol. Med., 1942, 49, 285- 

 289, and J. Exper. Med., 1942, 75, 

 489-494. A peak concentration is 

 reached in plasma 2 to 5 hrs. after inges- 

 tion when it falls off rapidly. The con- 

 centration in red cells continues to 

 increase over 2 days. 



Radioelement 85 (ekaiodine, 85-") half life 

 71 hrs. This element, which does not 

 occur naturally in anj'^ known form, has 

 been used by Hamilton, J. G. and Soley, 

 M. H., Proc. Nat. Acad. Sci., 1940, 

 26, 483-489) as a heavy homologue of 

 iodine in their studies on thyroid. 

 General behavior resembles iodine in 

 thyroid. 



Radiofluorine (Pi^) half life 112 min. 

 Volker, J. F., Sagnnaec, R. F. and 

 Bibby, B. G., Am. J. Physiol., 1941, 132, 

 707-712 studied distribution in rats and 

 cats after intravenous and intra- 

 peritoneal injection of radiofluorine salts. 

 Blood concentration falls rapidly as the 

 concentration in calcium containing 

 tissues rises. Ultimate concentration 

 in calcified tissues is in proportion to 

 their vascularity. 



Radioiodine (I"0 half life 8 days. A com- 

 parison of the rate of uptake of radio - 

 iodine, radiosodium, radiopotassium, 

 radiochloride, and radiobromide has 

 been made in normal human subjects 

 by Hamilton, J. G., Am. J. Physiol., 

 1938, 124, 667-678. The rateof gamma 

 ray emission from the hand is followed 

 after the subjects receive the salts by 

 mouth. This indicates the rate at 

 which the radiosalt enters the circula- 

 tion. Peak absorption is reached within 

 1^-2 hrs. for all except radiopotassium. 

 Its absorption continues to rise slowly 

 for 4 J hrs. 



The metabolism of iodine by the 

 thyroid gland in various physiological 

 and pathological conditions has natu- 



