Abstract
The hydrophobic property of crude samples of canine and porcine mucus was demonstrated by its binding and reactivity with two fluorescent dyes, 1-anilinonaphthalene-8-sulfonic acid (ANS) and 1,6-diphenyl-1,3,5-hexatriene (DPH). The contribution of lipids to these hydrophobic binding sites was indicated by our observations that the DPH-induced fluorescence of both porcine and canine gastric mucus was reduced > 75% after lipid extraction. Fluorescence microscopy revealed an extracellular band of intense reactivity in association with the mucus gel layer overlying the rat gastric mucosa that was abolished if the frozen sections were pretreated with lipid solvents. When rats pretreated with indomethacin were injected with a cytoprotective dose of 16,16-dimethyl-PGE2, there was an increase in fluorescence of the gastric perfusate treated with ANS, suggesting that hydrophobic factors, perhaps lipids, were being secreted in association with mucus. These extracellular lipids may play an important role in conferring protective barrier properties to the mucus gel layer.