H^■P()TH1•:RMI.\ AN'I) K 1 1 ).\' i: Y— ANUJ US 



219 



RAT 2 ''70^ 



1/c Na IL 



11/cNaP 



Lmiuiuimimmmmmmmmmmm 



(( ((( I Id Ml I I 



37°1 



TTTTT mm 

 _LL diuresis 

 T°rech 



Fig. 6. — Effect of hypothermia on spontaneous urine flow in a rat with ])ernianent diabetes 

 insipidus (hypothalamic lesion). "cXa P" = plasma concentration of radio-sodium; "cXa U" = 

 urinary concentration of radio-sodium. (The zig-zag line on the top of the radioactivity tracing 

 at 37° C. is the consequence of a mechanical arrangement preventing the excursion of the 



writing pen over the upper liorder of the smoked drum.) 



the pi I of whole l)lo()d. During waniiiny the urine again hecanie more acid. There 

 was very little titratal)le acid at any time. It should he pointed out that our animals 

 were mechanically ventilated throughout the experiment with room air at what was 

 calculated to he a normal minute volume. Ammonia prodtiction was sharply de- 

 creased during cooling. Initial urines contained an average of 48.6 mg. per cent and 

 at the depth of cooling 2.7 mg. per cent was present. This function returned as the 

 dogs were warmed. The concentration of Na and CI in the urine increased during 

 cooling to values closely approximating those of the serum, and returned to normal 

 during rewarming. Potassium concentration in the urine fell rapidly with cooling 

 to a valtie only three times that of the serum. The concentration of creatinine in the 

 urine fell from 116.9 mg. per cent initially to 7.S mg. ])er cent with cooling. 



Creatinine clearance fell markedly, hut Na and CI clearance rose as cooling 

 progressed. These were reversed with rewarming. Potassium clearance was un- 

 changed. 



Filtration rates were l)ased on endogenous creatinine clearance. The percent ex- 

 cretion of each filtered load was affected; PL,(). Na and CI paralleled each other 

 closelv from an initial value of 0.5 per cent at o7° C. to 12 per cent at 22° C. and 



