A quantitative immuno-electronmicroscopic study of amylase and chymotrypsinogen in peri- and tele-insular cells of the rat exocrine pancreas.

Malaisse-Lagae demonstrated in 1975 that peri-insular (PI) cells and tele-insular (TI) cells produce amylase (Am) and chymotrypsinogen (Ch) in a different ratio. These biochemical measurements are in contradiction with recent observations of Bendayan (1985), who found that the Am/Ch ratio measured with the protein A-gold technique applied to ultrathin Epon sections was the same in PI and TI cells. We have previously shown (Posthuma et al., 1984) that experimentally induced changes in Am and Ch content of rat pancreas are quantitatively reflected by immuno-gold labeling of zymogen granules in cryosections. Here we applied the same technique to compare the Am/Ch labeling density ratios in PI and TI pancreatic cells. To ascertain constancy of experimental conditions, we used ultrathin cryosections from tissue blocks consisting of TI and PI tissue elements. Consecutive sections of these blocks were alternatively immunolabeled for Am and Ch, using protein A-gold as marker. The density of gold particles over zymogen granules of both PI and TI cells was measured. It appeared that the Am/Ch labeling density ratio was significantly lower in PI than in TI cells. This difference resulted from a lower Am labeling as well as higher Ch labeling density over zymogen granules in PI cells.