RESORPTIOX RATE OF IXJECTED NaU"CO, 829 



we added in these experiments to each centrifuge bottle NaHCOg carrier before 

 collecting the precipitated BaCOg for assay of radioactivity. 



For determination of the total amount of exhaled COg per each 2-minute 

 period with this latter procedure no carrier was added. The precipitate was spvm 

 down and the supernatant solution was titrated to pTI ^^ 1, spun down and poured 

 off. After two washings witli ice cold CO._j free distilled water alcohol the precipi- 

 tate was dissolved in HCl and backtitrated with NaOH. 



In the X-ray experiments every second group of mice was, previous to injection, 

 exposed to 2000 r of 155 kv X-raj^s filtered by 1 mm Al, dose rate 140 r/min. in 

 the experiments where COj was collected in 10-minute intervals and 1350 r/min. 

 in those series collecting COj in 2-minute intervals. 



The data relevant to the hormone administiation aie given in connection 

 with the description of those experiments. 



RESULTS 

 Effect of X-Rays 



In a set of eight experiments the exhalation of the total amount of 

 COg and of ^'^COg from groups of each four irradiated and four control 

 mice was measured using the first arrangement described above. It 

 appeared that the irradiation slightly decreased the amount of CO2 

 exhaled (12 J^ 2.7%) as found by us previously. (l)The amount of ^^COg 

 (milligrams COgX relative specific activity) exhaled by the exposed mice, 

 however, was significantly greater (22.8 -^ 3.4%) than that given off 

 by the controls. The collection of COg was started between 15 and 30 mi- 

 nutes after the injection of the NaH^^COg, which followed immediately 

 upon the irradiation and was continued in 10-minute intervals for about 

 1 hour. No conspicuous changes in the percentage figures were found 

 during that time. 



Essentially, similar results were found when NaHC^^Og was injected 

 20 hours after the irradiation giving 18.7 -^ 2.4% less CO2 and 19.9 -^ 

 J^ 3.9% more -^^COg on an average. It appears, then, that these X-ray 

 effects persist for at least 1 day. It is possible, however, that this late 

 effect is of another character, being the result of a progressive irradiation 

 lesion. 



The enhanced exhalation of ^^COg might be expected to run parallel 

 with a smaller amount of residual ^^C in the irradiated animals. Analyses 

 of control and irradiated animals killed 40 minutes after injection showed, 

 however, that the activity of the homogenized and dried tissue did not 

 vary appreciably. Out of the injected 106,000 counts, 5060, i. e. 4.8%, 

 were found to be present in the controls and 4850, i.e. 4.6 %, in the 

 exposed mice. The enhanced exhalation of ^^C'Og by exposed animals 

 could thus not be due to an increased retention of ^^C by the controls. 



The only explanation left seemed to be that irradiated mice exhale 

 ^^COa at a markedly decreased rate for a very short period immediately 



