Stimulation of acid formation by histamine, carbachol and pentagastrin in isolated pig parietal cells

Abstract

Free cells were obtained by sequential incubations of pig gastric mucosa with pronase and collagenase. Approximately 10-15% of the cell population represented parietal cells. Accumulation of aminopyrine (AP) in the acid compartments of parietal cells was used as an index of their acid production. Histamine, carbachol and pentagastrin each independently stimulated aminopyrine accumulation. The initial rate of aminopyrine accumulation, observed after addition of 10(-4) M carbachol or 10(-6) M pentagastrin, were 32% and 10%, respectively, of that observed with 10(-4) M histamine. Steady-state aminopyrine accumulation in the presence of 10(-4) M histamine, 10(-4) M carbachol or 10(-6) M pentagastrin were 6.2 +/- 3.3, 2.6 +/- 0.6 and 3.0 +/- 1.5 pmol AP per 10(4) parietal cells, respectively (mean +/- SD, n = 5). The EC50 value for histamine was 3.4 +/- 1.4 X 10(-7) M, and for pentagastrin 5.9 +/- 4.2 X 10(-8) M (mean +/- SD, n = 5). The dose-response curve for carbachol was biphasic. A plateau was reached at 10(-5)-10(-4) M carbachol, and for this phase an apparent EC50 of 2.1 +/- 1.4 X 10(-6) M carbachol was calculated (mean +/- SD, n = 5). A further increase to 10(-3) M carbachol increased the aminopyrine accumulation. Atropine (10(-6) M) inhibited the response to concentrations up to 10(-4) M carbachol, but was without effect on the histamine- and pentagastrin-stimulation. The H2-receptor antagonist, cimetidine, right-shifted the dose--response curve for histamine. Also, the pentagastrin-stimulated aminopyrine accumulation was inhibited by cimetidine.(ABSTRACT TRUNCATED AT 250 WORDS)