Age-related stimulation by tetragastrin of gastric mucin biosynthesis in rat.

The effects of tetragastrin on gastric mucin biosynthesis in middle-aged rats were compared with those in young rats. The incorporation of [3H]glucosamine and [35S]sulfate into mucin was stimulated by tetragastrin in cultured corpus mucosa from 7-week-old rats. In contrast, tetragastrin could not enhance mucin biosynthesis in stomachs from 52-week-old rats. The isosorbide dinitrate-induced stimulation of corpus mucin biosynthesis observed in middle-aged rats was essentially the same as that seen in young rats. Nitric oxide (NO) synthase activity of the corpus was significantly reduced in the middle-aged rats compared to the young rats. NO synthase-immunoreactivity was observed at surface mucous cells in the corpus mucosa of young, but not of middle-aged, rats. These results suggest that aging decreases the effect of gastrin on gastric mucin biosynthesis through the age-related loss of NO synthase function in the surface mucous cell layer of rat stomach.