Mechanism of inhibition of gastric acid secretion by SCN-: interrelation of SCN- flux and inhibition.

Effects of thiocyanate (SCN-) and imidazole on acid secretion and Cl- flux across the isolated bullfrog gastric mucosa have been examined. For open-circuited mucosae, with Cl- Ringer on the nutrient side and 110 mM Na isethionate on the secretory side, the addition of 15 mM SCN- to either the secretory or nutrient side gave equivalent reductions in acid secretion (JH) and nutrient-to-secretory Cl- flux (JnsCl) . JnsSCN, the nutrient-to-secretory flux of SCN- (0.2 mu eq . cm-2 . h-1), was much less than the decrease in JH (1.88 mu eq . cm-2 . h-1). Addition of imidazole, phosphate, or histidine to the secretory side reversed SCN- inhibition of JnsCl. Addition of imidazole to the nutrient side gave equivalent restorations of JnsCl and JH. The increase in JnsSCN, 0.07 mu eq . cm-2 . h-1, was much less than the increase in either JH, 0.77, or JnsCl, 0.86 mu eq . cm-2 . h-1. Similar results were obtained for mucosae bathed with NaCl on the secretory side. With 15 mM SCN- on both sides, the flux ratio for Cl- was significantly larger (1.0) than the flux ratio for SCN- (0.47). The addition of nutrient imidazole increased the flux ratios for Cl- and SCN- to 1.29 and 1.16, respectively. Both SCN- and Cl- showed exchange diffusion. Inhibition of acid secretion with nutrient SCN- at short circuit also inhibited JnsCl but did not alter the partial conductance of Cl-.(ABSTRACT TRUNCATED AT 250 WORDS)