Effect of 20 weeks' ranitidine treatment on plasma gastrin levels and gastric enterochromaffin-like cell density in the rat.

In this study, the effect of ranitidine treatment on the activation and proliferation of rat gastric enterochromaffin-like (ECL) cells was investigated. The drug was given in a high dose in the food (1.7-1.8 g/kg/day) for 20 weeks. This dose corresponds to the high dose given in the ranitidine oncogenicity study performed by Glaxo. With this dose regimen ranitidine induced hypergastrinaemia for 10 h of the day. The duration and the extent of the hypergastrinaemia closely followed the occurrence of ranitidine in plasma, strongly suggesting that the hypergastrinaemia was secondary to inhibition of acid secretion. Following 20 weeks treatment with ranitidine, both the relative weight of the stomach and that of the oxyntic mucosa were increased. The oxyntic histamine concentration and ECL-cell density were also increased significantly. These results show that when ranitidine is given in the diet the resulting hypergastrinaemia, which had a duration of 10 h each day, leads to a general increase in the oxyntic mucosal weight and a proliferation and activation of the ECL cells, indicating that sustained hypergastrinaemia is not a necessary requirement for development of ECL-cell hyperplasia.