Free fatty acids stimulate mucin hypersecretion by rabbit gall-bladder epithelium in vitro

1. Mucin, a high-molecular-weight glycoprotein secreted by the gall-bladder and biliary duct epithelium, is a well-known nucleation-prompting factor in experimental and human gall-stone disease. 2. Free fatty acids when incubated in vitro (micellar suspension with 1 mmol/l Tween 40) with rabbit gall-bladders can promote abundant mucus secretion. 3. The hexosamine content of rabbit gall-bladder walls, measured by gas-liquid chromatography, was significantly higher in gall-bladders incubated with fatty acids than in control tissues. 4. The biochemical data were supported by ultrastructural findings showing numerous droplets with a translucent content in the perinuclear cytoplasm. Exocytosis was also seen in treated gall-bladders, confirming the secretory nature of the vesicles. 5. These results suggest that free fatty acids, which appear in high amounts when bile lecithins are hydrolysed by phospholipase, play an active role in the gall-stone formation.