208 



Theories of Secretion 



but Seeman was able to show transients at this time. The decline 

 in potassium output in the saliva is reflected in the depletion in 

 the total potassium in the gland which may amount to 40 per cent 

 of the initial content after only 3 minutes' stimulation (dog sub- 

 maxillary) ; a nearly equivalent amount of sodium is gained by the 

 gland. However, there is only a relatively small change in the intra- 

 cellular content of potassium because the intracellular space of 

 the gland shrinks considerably during stimulation (Burgen, un- 

 published). Most, but not all, of the increase in gland sodium is due 

 to the corresponding increase in gland extracellular space. A simi- 

 lar but rather smaller loss of potassium has been found in the cat 

 sublingual gland (Lundberg, 1958). The loss of potassium from 

 the gland during stimulation has also been followed continuously 

 by the balance method (Fig. 10.9) in which the venous effluent 



mm 



Fig. 10.9. The submaxillary gland circulation in a dog was isolated so that 

 the venous blood draining from the gland could be collected. Following a rest 

 period, the chorda tympani was stimulated at 20 c/s. 



Kv = venous plasma potassium in mEq/1. ; Ks = saliva potassium in mEq/1. : V = saliva flow- 

 rate in mg/g min; ABF arterial blood flow through the gland in ml/g min. Note that at the 

 beginning of stimulation the potassium concentration in the saliva was over 40 mEq/1., whereas 

 in the steady state it was only 6 mEq/1. At the beginning of stimulation the concentration of 

 potassium in the venous plasma reached over 11 mEq/1. and later settled down to 26 mEq/1. 

 (Burgen, 1956). 



