Metabolic Aspects of Ion Transport in the Foetal Gastric Mucosa

Abstract

The rabbit foetal gastric mucosa actively absorbs Na+ and secretes a small amount of acid. The mechanisms by which metabolic energy is utilized for active ion transport in this tissue were investigated.

The history and main theories of gastric secretion and oxidativephosphorylation were reviewed briefly. Na transport in amphibian and mammalian gastric mucosae was described and discussed.

Oxygen consumption, adenosine triphosphate, adenosine diphosphate, and creatine phosphate concentration changes and active ion transport in the rabbit foetal gastric mucosa were investigated in the presence and absence of exogenous glucose, during anoxia and reoxygenation and in the presence of ouabain, oligomycin, and dinitrophenol.

Investigation of the effect of the presence and absence of exogenous glucose suggested that the tissue contained an energy source other than creatine phosphate. It was also shown that creatine phosphate could however be used to some extent in adverse conditions, such as during anoxia.

Experiments on the effect of anoxia and subsequent reoxygenation showed that isolated foetal gastric mucosal cells were capable of resynthesizing adenosine triphosphate after large tissue concentration decreases of both adenosine triphosphate and adenosine diphosphate. However, ion transport did not seem to be solely dependent on the absolute tissue concentration of adenosine triphosphate. The adenosine triphosphate/adenosine diphosphate ratio also did not seem to be a direct controlling factor.

The effects observed with ouabain strongly suggested direct involvement of adenosine triphosphate in active Na+ transport, possibly through a (Na+ + K+)-stimulated adenosine triphosphatase. However, the effects of ouabain on acid secretion were thought to be indirect. The experiments with oligomycin and dinitrophenol showed that respiratory energy could not be utilized directly for active ion transport. A high-energy phosphorylated intermediate or adenosine triphosphate seemed necessary. Nevertheless, acid secretion seemed also to be dependent on oxidative processes.