EVALUATION OF THE TROPHIC EFFECT OF LONG-TERM TREATMENT WITH THE HISTAMINE H-2-RECEPTOR ANTAGONIST LOXTIDINE ON RAT OXYNTIC MUCOSA BY DIFFERENTIAL COUNTING OF DISPERSED CELLS

To evaluate whether the general trophic effect of gastrin on the oxynt ic mucosa is an indirect effect mediated by histamine H-2 receptors, s ustained 24 hour hypergastrinaemia was induced in Sprague-Dawley rats by treatment with the long acting and potent histamine H-2 antagonist loxtidine for five months. The trophic effect was assessed by weight, enumeration of total mucosal cells, parietal cells, and enterochromaff in like cells in smears stained for the actual cells after enzymatic d ispersion of the mucosa, and by biochemical analysis of oxyntic mucosa l homogenates. The weight of the whole stomach and the oxyntic mucosa increased by 12.7% (p=0.016) and 27.5% (p=0.006), respectively. Total oxyntic mucosal protein content increased by 28.7% (p=0.058). Total nu mbers of mucosal cells and parietal cells increased by 11.9% (NS) and 24.1% (NS), respectively. The amount of the parietal cell specific enz yme H+,K+-ATPase was unchanged. On the other hand, the number of enter ochromaffin like cells and related parameters, histidine decarboxylase activity and histamine content of the, oxyntic mucosa, showed a prono unced and significant increase. It is concluded that the general troph ic effect of gastrin on the oxyntic mucosa is not mediated by the hist amine H-2 receptor. The tropic effect of gastrin on the parietal cell seems, in contrast with that on the enterochromaffin Like cell, not to be specific but only reflecting the general trophic effect on the oxy ntic mucosa.