Age-related alterations of gastric mucosa and estrogen synthesis in rat parietal cells

The stomach has diverse functions other than gastric acid secretion. Multifaceted studies have investigated age-related changes of the gastrointestinal tract. Nevertheless, little is known about estrogen production changes in gastric parietal cells in rats aged over 3 months. We investigated age-related changes in gastric estrogen synthesis and the accompanying changes in liver estrogen receptor from 3 to 24 months. Weights of the body, stomach, and liver increased linearly from 3 to 18 months, then maintained a constant proportion up to 24 months. The gastric mucosa area (in mm²/1 mm muscularis mucosa) showed a constant proportion throughout the rats' life. The population of parietal cells immunostained area with H⁺/K⁺-ATPase decreased gradually with advancing age. Cells that were immunopositive to aromatase antibody were observed at 3-24 months. The expressions of aromatase mRNA and its protein were somewhat lower at 18 and 24 months than at 3 months. The portal venous estradiol concentration at 12 months was 1.5 times higher than that at 3 months, and that at 18 months was a half of that at 3 months. The expression of estrogen receptor mRNA in the liver at 18 and 24 months was about 80% of that at 3 months. Results suggest that the gastric estrogen production declines with aging, and the liver estrogen receptor is also affected accordingly. Simultaneously, the gastric mucosa continues to express aromatase to maintain liver function(s) throughout the animal's life.