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Theories of Secretion 



cent of that found in the controls (Fig. 10.7). Similar results were 

 obtained when chloride was replaced by thiocyanate or iodide. 

 These changes were readily reversed by restoration of chloride 

 to the perfusion fluid. However, it was not shown that the changes 

 were not due to a reduced sensitivity to acetylcholine rather than 

 to a reduced intrinsic ability of the membrane to respond ; further, 

 a similar reduction to response was seen when potassium was 

 omitted from the medium. Some of these experiments should be 



Fig. 10.7. Secretory response of the perfused cat sublingual gland to 1 ^ig 

 acetylcholine and its dependence on the anion composition of the perfusing 

 fluid. 



The control perfusion fluid contained 150 mEq/1. chloride, otherwise the chloride was replaced 

 partly or completely by nitrate. Abscissa: concentration of chloride in perfusion fluid (Lundberg, 

 1957c). 



repeated, using a range of acetylcholine doses to make sure that 

 the maximum response is really reduced. The reduced secretion 

 when all the chloride is replaced by nitrate is also difficult to 

 explain. It seems somewhat improbable that the active transport 

 process for chloride could carry nitrate, iodide and thiocyanate, 

 albeit at reduced efficiency. It would be most interesting to know 

 what happens when chloride is replaced by a bulky ion such as 

 sulphate. 



There is no question that this work is of the greatest importance 

 for the understanding of salivary secretion, but there are a number 

 of puzzling and interesting aspects of these findings which need 

 further exploration. For instance, the resting potential across the 

 outer surface of the sublingual cells averages —33 mV; that across 



