Thiocyanate and nitrite inhibit proton translocation in gastric mucosa

Isolated frog gastric mucosa was used to study the separation of formation of protons (or their precursors) from proton translocation by using various inhibitors. Both thiocyanate (SCN-) and nitrite (NO2-) inhibit the acid secretion in spontaneously secreting mucosa. The inhibition is reversed when the inhibitor is removed such that the excess acid secreted above baseline in the 'off'-period compensates for the amount inhibited in the 'on'-period. Both agents also inhibit the effect on acid secretion of pulse stimulation with histamine though to a lesser extent. Upon removal of the inhibitor, the total amount of acid secreted in excess of basal is equal to that observed with histamine alone. Likewise, metiamide, an H2-antagonist, also inhibits acid secretion with or without histamine. However, in contrast to SCN- and NO2-, removal of this inhibitor is without effect on the acid-secretion rate. These results indicate that both SCN- and NO2- inhibit the proton translocation rather than the formation of protons or their precursors as is the case with metiamide.