EN
The effects of extracellular K⁺ in relation to extracellular Ca²⁺ on acid production were studied. Studies were performed in vitro using isolated cells from rat stomachs, and acid production was indirectly determined by ¹⁴C-aminopyrine (AP) accumulation. In the absence of K⁺ in the incubation medium histamine-stimulated AP accumulation ratios were significantly decreased independently in the presence or absence of extracellular Ca²⁺. Under basal conditions, in the absence of extracellular Ca²⁺ , increasing concentrations of extracellular K⁺ enhanced AP accumulation ratios to significantly higher than those found in the presence of Ca²⁺. In histamine-, cAMP-, and carbachol-stimulated parietal cells, high K⁺ concentrations increased AP accumulation significantly less in Ca²⁺-free than in Ca²⁺-containing media. High K⁺ also induced significantly both an increase in cytosolic free Ca²⁺ concentration and ⁴⁵ Ca²⁺ uptake. The present results confirmed the importance of K⁺ in gastric acid production and suggested a role for Ca²⁺ as a modulator of mechanisms of parietal cell stimulation.