840 ADVENTURES IN RADIOISOTOPE RESEARCH 



An adrenaline dose increased to 10 y resulted, however, in a reaction 

 which was qualitatively and quantitatively similar to that observed in 

 our earlier investigation after administration of 2 y. Likewise, after 

 increasing the X-ray dose to 4000—5000 r a similar initial depression 

 of the resorption rate was observed as was found after 2000 r in the 

 first investigation. The influence of the ACTH-treatment was quantita- 

 tively the same on both the two occasions. 



No definite opinion can be expressed concerning the reason for the 

 change in the sensitivity of mice to exposure and to adrenaline adminis- 

 tration; whether it is based on seasonal variations (the first investigation 

 was performed in winter— spring, this second one in the autumn) or is 

 due to a genetical shift in the mouse strain (the animals were heterozy- 

 gots, although from the same farm). It is to be emphasized that a shift 

 occurred both in the response to exposure to X-rays as well as to adrena- 

 line administration. This observation suggests the existence of some 

 correlation between the response of the body to hormonal changes and 

 the effect of X-rays as far as the resorption and distribution of labelled 

 compounds is concerned. There remains considerable uncertainty con- 

 cerning the mechanism of the interaction particularly because the sen- 

 sitivity to ACTH-treatment was found to be quantitatively similar in 

 the two instances whereas the X-ray and adrenaline effect were disi- 

 milar. These findings have, however, a general implication in isotope 

 and other studies as rapid resorption and distribution processes in the 

 body may likely be influenced by the hormonal balance of the animal. 



Siunmary 



Exposure to X-rays, administration of adrenaline or ACTH were found to 

 influence the rate of resorption of injected labelled bicarbonate by mice as indi- 

 cated by the amount of ^^COg exhaled. When repeating the experiments half 

 a year later, 2 — 3 times as high X-ray dose and a 5 times higher adrenahne dose 

 had to be applied to obtain the same effect on ^^COg exhalation while no change 

 in the sensitivity to ACTH was observed. 



References 



A. FoRSSBEKG and G. Hevesv, Amer. J. Physiol. 180, 325 (1955). 



