Cl- requirement of acid secretion in isolated gastric glands

The dependence of acid formation, as measured by aminopyrine (AP) accumulation, on medium and intracellular Cl- was investigated in resting (10(-4) M cimetidine) and stimulated (10(-3) M dibutyryl cAMP) gastric glands isolated from the rabbit stomach. Intracellular Cl- concentrations (Cli-) were measured by the steady-state distribution of 36Cl-. In Cl- -free conditions AP accumulation was absent. Medium Cl- induced AP accumulation (AP ratio = 125) in stimulated glands with a K0.5 of 10.4 +/- 1.1 mM, equivalent to 18.0 +/- 1.2 mM Cli-, and had a small effect on resting glands (AP ratio = 6). With normal Nai+ and Ki+ maintained, similar results were obtained in stimulated glands treated with 10(-5) M amphotericin (ampho) and 10(-4) M ouabain (ouab), where the basal-lateral membrane was confirmed to be short-circuited with respect to Cl- pathways, i.e., medium Cl- and Cli- were equal. The K0.5 for Cl-i was 17.5 +/- 2.5 mM. In resting glands treated with ampho and ouab, AP accumulation increased linearly (no saturation was observed) with increasing Cl- (AP ratio = 35). These results suggest that stimulation activates a Cl- component in the secretory membrane and not in the basal-lateral membrane of the parietal cell. The K+ requirement of AP accumulation at a physiological Cl-i of 60 mM was also investigated in ampho- and ouab-treated glands. On stimulation the K0.5 for Ki+ decreased from 19.5 to 12 mM, coupled with a large increase in AP accumulation, indicating that stimulation also activates a K+ component in the secretory membrane.(ABSTRACT TRUNCATED AT 250 WORDS)