FUNDAMENTAL CELLULAR HETEROGENEITY OF THE EXOCRINE PANCREAS

Homogeneity in structure and function are broadly assumed to be charac teristics of the acinar pancreatic digestive enzyme-secreting tissue, In recent years, physiological studies have shown that the pancreas st ores the digestive enzymes in heterogeneously composed pools and relea ses them from these pools in a cyclic and secretagogue-specific fashio n. The cellular basis for pancreatic heterogeneity is unknown; classic al light and electron microscopic preparations appear homogeneous, We applied a panel of biotinylated lectins to pancreatic tissue sections; acinar cell glycoconjugates were localized in situ with peroxidase an d fluorescent techniques and lebin-gold complexes. The lectin-binding properties of both fasting rabbit and rat pancreas revealed extensive and specific heterogeneity of the acinar cell population, Light and el ectron microscopy demonstrated highly heterogeneous labeling of the zy mogen granule contents of specific acinar cells with the lectins Ulex europaeus agglutinin (UEA) and Erythrina cristagalli (EGA), which also showed perferential labeling of peri-insular acini, Other lectins als o demonstrated heterogeneous binding to specific cellular regions. The striking acinar cell heterogeneity confirms earlier predictions, and may eventually prove to be the cellular basis for the secretion of dif ferent enzyme mixtures from heterogeneous sources within the pancreas.