Histamine metabolism of the gastric mucosa following antrectomy.

1. Histamine metabolism of the gastric mucosa in rats subjected to antrectomy, antrectomy and substitution with pentagastrin and exclusion of the antrum has been investigated employing various in vivo and in vitro methods.2. Mucosal histamine formation after antrectomy fell to about one third, whereas after antrum exclusion histamine formation increased many-fold.3. After antrectomy, mucosal histamine content decreased, and increased after antrum exclusion.4. After total gastrectomy, (a) whole-body histamine formation was reduced to about half, as judged by determining histamine excretion, and (b) pentagastrin infusion did not increase histamine excretion, showing absence of histamine mobilization from extra-gastric sources. In rats with the stomach retained, infusion of pentagastrin induced a dose-dependent increase in histamine excretion.5. Kinetic studies in which [(14)C]histidine was injected and the resulting urinary [(14)C]histamine determined showed that on pentagastrin infusion after antrectomy newly formed histamine was initially mobilized to a larger extent than in the controls.6. Antrectomized rats were subjected to substitution treatment by three injections per day of pentagastrin. After 3 weeks of substitution, histamine excretion was considerably higher than without substitution. After 6 weeks of substitution, histamine excretion was about the same in the substituted antrectomized, non-substituted antrectomized and sham-operated groups. Neither time nor substitution could, however, normalize the excretion of histamine on pentagastrin stimulation after antrectomy.7. In non-substituted antrectomized rats, pentagastrin was less effective in elevating mucosal histamine formation than in the substituted and sham-operated groups.8. The indispensability of the rat in this kind of study is emphasized.