EFFECTS ON PERMEABILITY AND ACTIVE TRANSPORT 



915 



cose is the substrate is inhibited by p-MB, one SH group being involved 

 here, but it is unlikely that glycolytic inhibition is the mechanism by which 

 acid secretion is depressed, inasmuch as inhibition occurs when pyruvate or 

 acetoacetate is the substrate. Respiration associated with secretion is also 

 inhibited by p-MB; it was felt that this is not a generalized effect on oxi- 



72 



63 



0.54 



0.45 



27 



09 



CARBACHOL (0 1 MG X) 



0.2 0.4 0.6 0.8 1.0 1.2 1.4 18 



Fig. 7-42. Inhibition of gastric acid secretion by 



p-MB, in the presence of 20 raM glucose and in 



the absence and presence of carbachol. (From 



Davenport et al., 1954.) 



dative reactions, but that the site of attack is some unknown system inti- 

 mately concerned with the secretory process. The relation between the inhi- 

 bitions of respiration and secretion by p-MB is reasonably linear (Fig. 7-43), 

 in contrast to the results with antimycin and 2,4-dinitrophenol (Davenport 

 and Chavre, 1956). Possibly the primary inhibition by j^-MB is on the trans- 

 port system itself, the respiration being reduced secondarily. Other SH 

 reagents inhibit secretion but apparently act at somewhat different sites 

 than p-MB (Davenport et al., 1955), so that it is difficult to correlate the 

 blockade of SH groups with the secretory suppression or to locate exactly 

 these SH groups. 



