Secretin dissipates red aridine orange fluoescence from pancreatic duct epithelium

This study was undertaken to elucidate whether duct cells in the pancreas contain acidic cytoplasmic compartments regulated by secretion. Microdissected pancreatic ducts from pigs were examined by acridibe orange (AO) and 2′, 7′-biscarboxyethyl-5(6)-carboxyfluorescein/tetraacetioxymethyl ester (BCECF/AM) epifluorescence microscopy. Estimated cytoplasmic pH using BCECF fluorescence was 7.43pL0.04 and was not changed by altering CO₂ tension in the incubation mdium. The epithelium of acridine orange incbated peripheral interlobular pancreatic ducts exhibited green and fluorescence was sen in resting pancreatic ducts and was greatly accentuated by raising CO₂ in the incubation medium with chloroqyuine or NH₄Cl or the protonophores carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) or carbonyl cyanide M-chlorophenylhydrazone (CCCP), leaving uniform gren fluoresence. These findings suggest that pancreatic duct cells contain CO₂-dependent acidic compartments which vanishduring seceatin stimulation and which may be cytoplasmic tubulovesicles.