Eelctron microscopy of unstained fresh air-dried spreads of mouse pancreas acinar cells and energy dispersive x-ray microanalysis of zymogen granules.

Electron microscopy of unstained, fresh air-dried spreads of the mouse pancreas has disclosed various substructures of acinar cells. The nucleus with a nucleolus, rough endoplasmic reticulum with ribosomes, mitochondria with dense granules, lysosomes, intracisternal granules, and zymogen granules with a core surrounded by a halo, and a boundary membrane were observable under a conventional electron microscope. Five zymogen granules of an acinar cell were examined by energy dispersive X-ray microanalysis. Peaks for phosphorus, sulfur, chlorine and potassium were detected in all of the zymogen granules examined, which confirmed a previous report (Takaya, 1975b). By increasing the integrated pulse counting time up to 300 seconds, calcium and magnesium were detected in two of the granules in addition to the elements mentioned above. No peaks for either copper or zinc were observed when nylon grids were used. The electrolyte content of zymogen granules and of acinar initial fluid is discussed in relation to the secretory mechanism of the exocrine pancreas.