GENERAL METABOLISM— HORXATH and SPURR 19 



hand, incmini;" louiul no .significant change in ])la.snia concentrations of calcium 

 at rectal teniperatin-es of 20° C. 



1"lu' role ol calcitini in hypothermia is undefmed at present hut may he of impor- 

 tance hecause of its well known power of offsetting the toxic properties of potas- 

 sium/'' In this connection, the protective elifect of injections of calcium against 

 suhsecjuent administration of potassium to hypothermic rats has already been men- 

 tioned.^" The literature on the effects of calcium on the physiology of the cell is 

 voluminous. °^ 



Magnesium. Platner and Hosko^* observed a linear increase in serum mag- 

 nesium with reduction of the rectal temperatures (jf the dog, cat, rat, hamster, and 

 turtle. On the basis of Heilbrunn's statement that cold "releases calcium into the 

 cell interior" they postulated that magnesium ions were thereby displaced and 

 passed not only to the cortical protoplasm, but out of the cell. Contrary to these fmd- 

 ings are those of Fleming-*^ and McMillan ct al.*- who observed no significant 

 change in the serum magnesium of the dog during hypothermia. However, these 

 observations were made at much lower rectal temperatures than those obtained for 

 the dog in Platner and Hosko's experiments. It may be that there is an initial in- 

 crease in serum magnesium in the dog followed by a reduction to near control levels 

 as the rectal temperature is progressively reduced. However, this does not explain 

 the increased serum magnesium levels observed in other homiothermic animals.^* 



Cations. Chloride, phosphate and bicarbonate have been determined during hypo- 

 thermia by several investigators. Swan et al.^^ found no change in serum chloride 

 that was not ascribable to the hyperventilation, Fleming," Deterling ct al.*^ and 

 Woodruff-^ observed no significant change at low rectal temperatures while Osborn*^ 

 reported a slight decrease. Earlier, Barbour, McKay and Griffith'^"'' described an 

 initial increase in serum chloride upon cooling of monkeys and rats to rectal tem- 

 peratures of about 30° C. This initial peak was preceded by a depression which the 

 authors believe may have Ijeen the result of an epinephrine effect. Upon further 

 cooling of the animals to 23° C. the serum chloride concentration approached or 

 attained the control levels. This is in agreement with the finding of no change from 

 control levels after variable periods of time below 27° C.-^ and no cliange consist- 

 ently at rectal temperatures of 20° C.*^ 



The serum phosphorus was found to decrease slightly by Swan ct al.^" who sug- 

 gested that there may be a movement of l)Oth phosphorus and potassium into body 

 cells in association with a disturbance in carbohydrate metabolism. Fleming," on 

 the other hand, found no significant change in the serum phosphate at rectal tem- 

 peratures of 20° C. 



It was observed by Osborn*"' that a low serum bicarbonate was associated with 

 the subsequent occurrence of ventricular fibrillation or with the appearance of a 

 'current of injury' in the electrocardiogram. By maintaining a high serum bicarbon- 

 ate throughout the hypothermia he was able to effect complete recovery in some 

 animals from rectal temperatures below 19° C. The effects associated with changes 

 in the serum bicarl)onate appear to be directly related to pH changes rather than 

 to bicarbonate per sc. This will be discussed later. Fleming" reported an increase 

 in bicarbonate at rectal temperatures of 20° C. which were not great enough to com- 

 pensate for the concomitant retention of CO.. He injected sodium bicarbonate to 



