Effect of a milk diet on rat gastric mucosa: receptor activity, histamine metabolism and ultrastructural analyses.

A bovine milk diet (BM) resulted in remarkable changes in histamine H2 receptor activity (sensitization) and PGE2 receptor activity (desensitization) in gastric glands isolated from adult rats. In contrast, the receptor-cAMP systems sensitive to glucagon(s) and secretin in parietal cells and muco-peptic cells were unaffected. In the two experimental groups, cimetidine produced a parallel displacement of the histamine dose-response curve suggesting competitive inhibition between this classical H2 receptor antagonist and histamine. The BM diet reduced the histidine decarboxylase activity in rat gastric mucosa; the histamine content was not significantly different in control and BM-fed rats. There was no alteration of the circadian rhythm of the parietal cell (ultrastructural changes: microvilli, tubulo-vesicles) determined at intervals of 6 hours in milk-fed rats. Prostaglandins and other components in milk (EGF, somatostatin, etc.) might therefore protect gastric mucosa by a differential control of PGE2 and histamine H2 receptor activity, either directly (PGE2 and EGF in milk) or indirectly (inhibition of endogeneous histamine synthesis/release and stimulation of prostaglandin synthesis/release).