Acid formation by permeable gastric glands: enhancement by prestimulation

Digitonin was used to render isolated gastric glands permeable. This procedure was found to release cellular lactic dehydrogenase without disrupting the parietal cell's ability to generate proton gradients. Optimal conditions for permeabilizing the glands were found to depend on the ratio of digitonin to gland concentration. Stimulation of the glands with histamine, forskolin, or 8-bromo-cAMP prior to digitonin treatment resulted in a marked enhancement of the subsequent ATP-dependent acid formation. This enhancement was not found with the cholinergic agonist carbachol. These results indicate that preservation of the active secreting state does not require the continued presence of soluble factors. Characterization of the ATP-dependent acid formation in prestimulated permeable glands showed a dependence on exogenous substrate and inhibition by the mitochondrial inhibitors oligomycin and atractyloside. Moreover, it was found that ADP could replace ATP in promoting acid formation. These results are interpreted to show that mitochondrial oxidative phosphorylation can serve as an in situ ATP-recycling system to provide a local supply of ATP for proton transport. The overall study demonstrates that the digitonin-permeabilized gastric gland preparation is a valuable model system for studying mechanisms of gastric proton transport.