RENAL FUXCTIOX— MOVER, XrORRIS and DE BAKEY 



203 



reduced to this extent ( hy nuiiierous iiuthods) there is usually a very dramatic 

 reductiDn in water and sodium excretion. In the current experiments, when the 

 temperatui-e was rechiced to .^0 to M C". there was actuall\- an inciease in water 

 excretion to 1 4.> per cent of the control \alues at the same time that s^lomerular 

 lihration rate was refhiced to 5S ])er cent of the control vahie.s. ( ihservations made 

 at a temperature of 2? to 17° showed little additional effect on scxlium and water 

 excretion, althous^h potassium excretion decreased to 63 per cent of the control 

 values. 



There was no consistent effect on ])lasma sodium and potassium. nes])ite a reduc- 

 tion in glomerular hitration rate and renal hlood flow, sodium and water excretion 

 were not reduced, which suggests that hypothermia depresses tuhular enzymatic 

 activity and thus reduces the reahsorptive capacity of the renal tubules. The effect 

 on potassium excretion further supports this concei)t since under normothermic 

 conditions potassium is actively excreted hy the renal tuhules. ddie reduction in 

 potassium excretion with a concurrent increase in sodium and water excretion leads 

 to the conclusion that enzymatic processes responsible for real)sor])tive and secre- 

 tory mechanisms are depressed during hypothermia. 



The effect of prolonged hypothermia at 25 to 27° C. is summarized in figure 4. 

 It is obvious that prolonged hy]:K)thermia had no additional effect on renal hemo- 

 dynamics. After two hours of hypothermia, the depression in blood pressure, 

 glomerular filtration rate, and renal blood flow was about the same as it was im- 

 mediately after the reduction in temperature to these levels. These observations 

 indicate that the depression in renal function is a direct response to the hypothermia 

 and the degree of hypothermia rather than to the length of time the animal is kept 

 at reduced temperatures. \\\\tn the temperature is again raised to control levels 

 there is an immediate increase in blood pressure back to the control levels. How- 



"o 



Mean Blood Pressure 



Glomerular 



Filtration Rote 



cc./min 



Hypothermio 



After 2 hours at 80° P 



Normof tiermio 



Renal Blood Flow 

 cc./min. 



Fig. 



mm. Hg 



-Tlie renal hemodynamic effect of liypotliermia immediately after reduction in temperature 

 com])ared to the responses observed after two hours of maintained iiypothermia. 



