RESORPTION RATE OP INJECTED NaH'^COj 833 



a manner which is mainly contrary to that of ACTH. The output of 

 i^COa (Table 2B, group 1) is markedly decreased in association with a 

 possible slight increase in the total amount of COg (group 2). The latter 

 figure is, however, not statistically significant. The combination of 

 adrenaline and irradiation, administering adrenaline 5 — 15 minutes 

 before the irradiation, gave a rather unexpected result. Instead of an 

 additional decrease in the output of ^^COa over that resulting from the 

 application of one of these two agents alone, an increased output was 

 obtained (group 3). Determinations of the total amount of exhaled 

 C'Og in this combined treatment gave a quite normal figure (group 4). 



Discussion 



The COg of the circulating bicarbonate is in rapid exchange equilibrium 

 with the CO2 of the alveolar air. Consequently, after an initial stage 

 following injection of labelled bicarbonate, the specific activities of the 

 blood CO2 and that of the expired air become identical. 



Apart from exhalation, which represents its main route, numerous 

 competitive routes are open to the ^^COg in the animal body. '^COa 

 finds its way into almost any organic body constituent. The injected 

 NaH^'^COa gives off its I'^COa to the alveolar air so rapidly, however, 

 that only a small amount is incorporated into the tissue constituents. 

 We found 40 minutes after the administration of labelled bicarbonate 

 the body of the mouse to contain 4.8% of the injected i*C. Skipper 

 etalS^'^^ record the presence after the lapse of 25 hours of 1.37% and 

 after 12 weeks of 0.12% of the total dose injected. The share of the 

 muscles in the total body ^^COg amounts after 25 hours to 41% and 

 after 12 weeks to 27%. For the skeleton, the figures given by Skipper 

 were: 18% is present after 25 hours and 23% after 12 weeks. The skeleton 

 gives off its '^COg at a lower rate than the muscle or any other organ 

 with the exception of the skin and hair. Armstrong etalS^^ found half 

 of the ^^COg incorporated into the skeleton of the rat after the lapse of 

 8 days still to be present after 1 month. 



We found the rate of exhalation of ^^COg following intraperitoneal 

 injection of NaRi^COg to be markedly depressed after exposure of the 

 mouse to 2000 r while that of total COg was depressed only slightly. 

 After intravenous injection of NaHi^COs the amount of ^^COg expired 

 by the irradiated mouse is not depressed to any marked extent. It is 

 thus the rate of resorption of sodium bicarbonate which is diminished 

 through exposure. Due to the extreme rapidity of the exhalation process, 

 the blocking effect of the irradiation on the rate of resorption of H^^COa 

 is only observable very briefly after the injection of the labelled bicar- 

 bonate. Thus, these X-ray effects may not be detected if the collection 

 of the expired COg is not started immediately after injection. 



5 3 Hevesy 



