104 



M. A. ROTHENBERG 



VOL. 4 (1950) 



The exchange of K was studied under identical conditions (30 min exposure at 

 22° and 13° C) using 0.013 M K^2(;;i instead of K39(3i ^j^ ^j^g ggg^ water. At 22° C the 

 average of seven nerves was 1.31 milhmoles/ioo g and at 13° C the average of the same 

 number of nerves was 1.09 milhmoles/ioo g (Table V). This would correspond to a 

 Qio of 1.33- 



TABLE V 



EFFECT OF TEMPERATURE ON THE RATE OF PENETRATION OF K 



Nerves exposed for 30 min to sea water at 22° C and 13° C containing 0.013 M K^^ci. Sj and Sg 

 = standards. 



The values for the Q^q obtained above for both Na and K are in good agreement 

 with the theoretical value of 1.25 calculated from ionic conductivity measurements. 

 The ionic velocities increase by about 2 to 2.5% for every degree rise of temperature''. 

 It is, therefore, possible that no important energy yielding chemical reactions are 

 involved in the exchange of ions across the nerve membrane under these experimental 

 conditions. 



2. Electrical activity and Na exchange. Stimulation of nerves by supramaximal 

 shocks while being perfused with sea water containing 0.39 M Na^^Cl + 0.13 M Na^^Cl 

 produced a marked alteration in the rate of exchange of Na when compared to resting 

 nerves. As described under Methods, nerves were mounted in plastic chambers in which 

 stimulating and recording electrodes were imbedded. The nerves were stimulated at a 

 rate of 100 times per second for 30 min. Only those nerves which exhibited normal 

 responses throughout this period of stimulation were analysed. Analysis of the axoplasm 

 of six of these nerves indicated that 15.9 millimoles Na/ioo g (mean value) had exchanged 

 within 30 min as compared with 9.5 millimoles/ioo g at rest. This would correspond to 

 an increase in the rate of exchange of approximately 67% above that at rest. The results 

 of the individual analyses are recorded in Table VL 



If the cation molarity (Na plus K) of the Squid axoplasm is a constant, as is sug- 

 gested by the work of Steinbach and Spiegelman, then it is evident that during nerve 

 References p. 114. 



