Mechanisms of stimulation of acid production in parietal cells isolated from the pig gastric mucosa.

Sequential incubations with pronase and collagenase of pig gastric mucosa resulted in single cell preparations containing 10-20% parietal cells, which could be enriched further to 85-95% purity by density-gradient centrifugation followed by elutriation. Acid production of the isolated cells was measured by means of aminopyrine accumulation in their acid compartments. When small pieces of the mucosa were pretreated for 1 h in the presence of either histamine, pentagastrin or carbachol before preparation of cells, the ability of the subsequently isolated cells to produce acid was increased. In parietal cells isolated from resting (not pretreated) mucosa pentagastrin, carbachol and also adrenaline increased the histamine-stimulated aminopyrine accumulation (50-90% increase). Adrenaline alone had no significant effect on the aminopyrine accumulation. In the presence of 10(-4) M histamine the apparent EC50 for adrenaline was 5 X 10(-7) M. Adrenaline, histamine, forskolin and isobutylmethylxanthin (IBMX) increased the formation of cAMP in purified parietal cells. The three 'classical' secretagogues histamine, pentagastrin and carbachol, but also IBMX and forskolin, increased the cytosolic free Ca2+ from approximately 1.5 X 10(-7) M to 2.2-3.5 X 10(-7) M but adrenaline and dibutyryl cyclic AMP did not. Thus the present results indicate that there are - in addition to histaminergic H2 receptors - specific cholinergic, gastrinergic and adrenergic receptors on the plasma membrane and that there are separate cAMP and Ca2+-dependent stimulatory pathways in the parietal cell.