Secretion of Intrinsic Factor from Cultured Rat Gastric Chief Cells

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Intrinsic factor (IF) is a vitamin B₁₂ binding protein that is secreted from the gastric mucosa. We tested secretagogues which stimulate IF secretion in rat gastric perfusion and found that carbachol and cholecystokinin octapeptide (CCK-8) stimulated secretion, but histamine and tetragastrin did not. To confirm these results, we examined IF secretion from isolated rat chief cells. For this purpose, we established an enzyme immunoassay (EIA) using an avidin-biotin peroxidase complex to measure small amounts of IF. To prepare an anti-rat IF, IF was isolated from the stomach, and was injected into a rabbit for immunization. Rat gastric chief cells were isolated from the gastric mucosa with Dispase and a Percoll gradient centrifugation, and were cultured. We examined the effects of chemicals by adding them to culture dishes of chief cells in a CO₂ incubator. Released IF in culture medium was determined by EIA. Carbachol, CCK-8 and secretin stimulated IF secretion from cultured chief cells, while histamine and tetragastrin did not ; Forskolin and A23187 also stimulated the secretion. We concluded that carbachol and CCK-8 stimulated IF secretion via an increase of intracellular Ca²⁺ concentration and that secretin did so via a cAMP accumulation.