A sexual dimorphism in gastric acid secretion has been known for many years, with women secreting less acid ( approximately 40%) than men. The mechanisms mediating this sex difference are unknown, but a role for estrogens is suggested from animal models. Two estrogen receptor (ER) subtypes, ER alpha and ER beta, mediate genomic effects of estrogens, and mRNA for both subtypes has been detected in the rat stomach. The objective of this study was to determine the cellular distribution of ER alpha and ER beta proteins in the rat stomach. ER alpha and ER beta proteins were detected in nuclei of fundic parietal cells and epithelial cells in the progenitor zone. In the antrum, several cells were immunoreactive for ER beta in regions containing stem and neuroendocrine cell types but ER alpha protein was not detected in antral glands. Both ER alpha and ER beta proteins were expressed in enteric neurons within the nucleus and cytoplasm, with specific punctate staining for ER alpha in cell bodies and fibers. These studies are the first to show differences between ER alpha and ER beta proteins in the epithelial cellular distribution in the fundus and antrum and to detect co-expression in enteric neurons. These results suggest that estrogens may inhibit gastric acid secretion via genomic effects in fundic parietal cells through either ER subtype and in antral neuroendocrine cells via ER beta. Moreover, co-expression of ER alpha and ER beta in enteric neurons indicates that estrogenic effects could also be mediated through neurogenic reflexes. Our findings imply that direct regulation of multiple cell types by estrogens may contribute to the modulation of gastric functions that have been recognized during the estrous cycle and between the sexes.

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