COMPARTMENTALIZATION OF SECRETORY PROTEINS IN PANCREATIC ZYMOGEN GRANULES AS REVEALED BY IMMUNOLABELING ON CRYO-FIXED AND MOLECULAR DISTILLATION PROCESSED TISSUE

Immunogold labeling of amylase obtained over zymogen granules of rat p ancreatic acinar cells processed through cryofixation, molecular disti llation drying and embedding in resins was found to be of high intensi ty and displayed a particular pattern. Indeed, it was concentrated in certain areas of the granules leaving others devoid of gold particles. This pattern of labeling reflects a strong compartmentalization of th e secretory proteins within each granule. In order to assess this phen omenon, we have compared the intensities and the pattern of distributi on of the labelings in tissues processed through: chemical fixation wi th embedding in various resins, cryo-ultramicrotomy and cryo-fixation followed by molecular distillation drying. Serials sections and double labeling experiments were performed for further evaluation of the res ults and for assessing artefactual displacement of proteins during tis sue preparation. The results obtained indicate that the secretory prot eins are indeed segregated within the granule which appears thus as a well organized structure. Cryo-fixation combined with molecular distil lation appears thus to be superior in terms of preservation of protein antigenicity and retention of cellular components close to their livi ng state.