Certain parameters of secretory activity of the pancreatic acinus as a system consisting of separate cells were verified at the electron microscopic level. Thirty male Wistar rats were investigated; they were sacrificed by one every 49 min for 3 days. Volumetric portion of the condensing vacuoles, zymogen granules and all granules of the secrete within the limits of the cytoplasm zone, where these granules were present, as well as number of the granules and an average volume of separate condensing vacuoles and zymogen granules were estimated. The results of measurements were smoothed out by the method for calculating the sliding averages in order to expel frequent oscillations with the period up to 5 hours. Changes in the exported proteins reserves at various phases of the secretory cycle were obtained by fluctuations in the secreted granule numbers and their individual volumes. After an ecologically adequate feeding in the evening, the number of the condensing vacuoles increased, and then, in 1-1.5 h did the number of the zymogen granules. Increase in the cell synthesizing activity also resulted in increasing average volume of separate condencing vacoules and zymogen granules. The rhythmicity of different parameters characterizing the secretory process was coordinated, that demonstrated certain synchronization of individual secretory cycles in separate cells, nevertheless, it was not complete, since for synchronization of the whole population of the acinar cells at the stage of the zymogen granules maturation it was necessary 0.5-1 hour.