C. ADRIAX M. HOGBEN IQI 



to the uncertainty in calculating the energetic elBciency of hydrochloric acid 

 secretion. The endogenous production of lactate ion requires that its contribu- 

 tion to ionic movement across the mucosa be evaluated. Under the conditions 

 used to study chloride transport it is insignificant (47). The small amount of 

 lactate accumulates preponderantly in the serosal solution bathing the isolated 

 mucosa (14, 26, 47). 



Glucose is a recognized substrate capable of sustaining the activity of the 

 isolated gastric mucosa, but it is not unique; acetoacetate (16), lactate or 

 pyruvate (15) is adequate for continuous acid secretion. The H+ secretion of 

 isolated mucosae from thiamine deficient mice is reduced to half and accom- 

 panied by a measurable increase in pyruvate accumulation, which is greater 

 in the nutrient than in the secretory solution (21). However, the ability of 

 these stomachs to consume pyruvate was not appreciably diminished. 



Anaerobiosis and injurious inhibitors (cyanide, dinitrophenol, azide, etc.) 

 have been applied to the isolated mucosa without evoking unique responses. 

 They abolish the spontaneous potential (mucosal current?), markedly lower 

 electrical resistance and halt hydrogen ion secretion (22, 23). These are not 

 une.xpected findings for an organ with a very active metabolism, much of which 

 is required for active ion transport. Crane and Davies (7) report a transitory 

 rise of mucosal resistance after exposure to 1.5 mM/1. iodoacetate. 



Two observations reported by Davenport suggest that there may be a qualita- 

 tive metabolic change when the spontaneously secreting isolated stomach is 

 stimulated by histamine or carbaminoylcholine. The concentration of aceto- 

 acetate, as the exogenous substrate, does not influence the spontaneous secre- 

 tion rate but does determine the increased secretion rate in the isolated mucosa 

 elicited by carbaminoylcholine or histamine (14). P-chloromercuribenzoate in- 

 hibits the increase due to stimuli but the range of its effectiveness is limited 

 by solubility (19). 



The rate of secretion of the isolated mucosa is sensitive to temperature. 

 An activation energy of 22,000 calories per mole has been calculated for the 

 isolated frog mucosa (94). The complex nature of the temperature response of 

 the isolated mouse mucosa led Davenport to the conclusion that the informa- 

 tion at hand did not warrant calculation of the 'activation energy' of HCl 

 secretion for this preparation (18). 



There has been considerable interest in a possible role for gastric epithelial 

 urease (5). There is no stoichometric relation between urease activity and H"*" 

 secretion (38) and the gastric urease activity is probably a bacterial artifact 



(29, 56)- 



Further details concerning the cellular metabolism of gastric secretion can 

 be found in recent reviews (it,, 41). At present we are limited to the knowledge 

 that aerobic metabolism is necessary to sustain secretion and that no reaction 

 in the respiratory pathways can be singled out as unique. Though the mode of 



