D. C. TOSTESON 



145 



pared with fresh cells. K transport is also slowed during prolonged incubation 

 in Xo in the presence of glucose, and in C)^ in the presence or absence of glu- 

 cose, but the effect is much less striking. After 20 hours' incubation in the 

 j)resence of glucose, K transport is faster in O2 than in N2 . This slowing down 

 of K transport after 20 hours' incubation in the absence of substrate in No can- 

 not be reversed by addition of glucose and/or equilibration with O-. . 



c) Effect of inhibitors. We will limit our discussion here to the effects of in- 

 hibitors on K influx in duck cells incubated in N2 . This restriction is imposed 

 both because the interpretation of inhibitor experiments is somewhat easier 

 in the simpler gh-colyzing system than in the more complicated respiring cell, 

 and because of the evidence cited above that K transport is more active in N2 . 



Sodium iodoacetate (lAA) in a concentration of i mn/l. completely blocks 

 lactate production and reduces K influx to about one-half of its normal value 



Table 4. Effect of iodoacetate and fluoride on k transport in duck red cells 



Duck red cells were incubated in 95% Nz-5% CO2 at ^,^°C in a medium containing glucose 

 as substrate. 



in duck cells incubated in X2 (table 4). K outflux is affected only slightly. 10 

 mM/1. lAA produced no further fall in K influx. 



On the other hand, 30 mM/1. sodium fluoride (NaF) also markedly inhibits 

 lactic acid production, but increases K influx four-fold in duck cells incubated 

 in No (table 4). K outflux must be increased by an equal amount since there 

 is no appreciable change in the K concentration in the cells. 10 mM/1. NaF 

 blocks glycolysis only partially but also stimulates K influx. In the presence 

 of 30 mM/1. NaF, cell sodium increases slightly more rapidly than it does in 

 the presence of i mM/1. lAA. These effects of NaF are observed no matter 

 whether the inhibitor is added in addition to the usual medium or in replace- 

 ment of NaCl. The effect also occurs in the presence and absence of plasma. 

 If 30 mM/1. NaF and i mM/1. lAA are both present, the NaF effect predom- 

 inates and K influx is somewhat increased. 



I mM/i. 2,4-dinitrophenol stimulates glycolysis but substantially reduces 

 K influx. 0.1 mM/1. dinitrophenol, i mM/1. sodium cyanide, 5 mM 1. arsenate, 

 I mM/1. sodium azide and 50 mM/I. nicotinamide do not appreciably affect K 



