The Source of a Gastric Secretory Inhibitor From Human Saliva

Abstract

Summary The contribution made by oral bacteria to the content of substances in human saliva which inhibit rat gastric acid secretion on intravenous injection was assessed. It was found that, when growth of bacteria in saliva was prevented, the saliva had no capacity to inhibit rat gastric acid secretion, whereas when no antibacterial precautions were taken for three hours saliva did possess such activity. It was found that oral bacteria cultured free of saliva possessed the capacity to inhibit gastric acid secretion. Three oral bacteria (Neisseria catarrhalis, α‐hæmolytic Streptococcus spp. and Lactobacillus casei) were studied in detail, and were found to inhibit rat gastric acid secretion to 50% of control values in doses of 400 to 800 μg. per kilogram. Studies on fragmented bacteria indicated that inhibitory activity resided in the supernatant fraction derived mainly from the bacterial cytoplasm. Preparations of bacterial cell walls were without any inhibitory activity. It was shown that the effect on gastric acid secretion was not due simply to the embolic effects of bacterial injection, and it is concluded that the phenomenon is probably due to a specific metabolic effect of a bacterial cell component.

Mastication and acid secretion

“…This study shows that saliva alone has little effect on the pH of a standard diet, corroborating the findings of Baume (1968). Similarly, there is no difference in the gastric acid response to a masticatory or a non-masticatory diet.…”