Insulin receptor-related receptor messenger ribonucleic acid in the stomach is focally expressed in the enterochromaffin-like cells.

The insulin receptor-related receptor (IRR) is a member of the insulin receptor family. In contrast to the widespread expression of insulin receptor and insulin-like growth factor-I receptor messenger RNA (mRNA), the expression of IRR mRNA is highly restricted to the kidney and stomach. IRR mRNA in the kidney is focally expressed in the renal distal tubule cells. However, the cellular localization of IRR mRNA in the stomach remains to be elucidated. Here, we examined the cellular localization of IRR mRNA in the rat stomach by in situ hybridization. IRR mRNA in the stomach was abundantly localized in the basal third of the oxyntic glands of the fundic stomach. IRR mRNA in the stomach was colocalized with mRNA for histidine decarboxylase, a marker for the enterochromaffin-like (ECL) cells, indicating that the expression was restricted to ECL cells. ECL cells actively produce and store histamine, which is an important physiological stimulant of acid secretion from the parietal cells. The preferential localization of IRR mRNA in ECL cells suggests that the IRR plays an important role in the function of these cells.