[Diurnal rhythm of lysosomal organelle decomposition in liver, kidney and pancreas].

The amount of autophagic vacuoles which, under certain presumptions, can be used as a measure of the intensity of cellular autophagy shows clear cut diurnal changes in untreated rats. Liver parenchymal cells, epithelial cells of proximal convoluted tubules of the kidney, and acinar cells of the exocrine pancreas were investigated. The rhythm is synchronous for these three cell types. The "maximum" was found during the light period, the "minimum" during the dark period. The quantitative findings are in keeping with the assumption that cellular organelles are destroyed exclusively by cellular autophagy. Different turnover rates of mitochondrial and peroxisomal constituents, as determined in biochemical experiments, are paralleled by different relative frequencies to which mitochondria and peroxisomes occur in autophagic vacuoles. In liver cells the physiological rhythm can be influenced by alteration of feeding conditions. It is inverted when a single daily meal is fed in the first half of the light period. In early starvation the level of the diurnal "maximum" of cellular autophagy continues for the first hours of the dark period until a slow decline takes place. Cellular autophagy is completely stopped for several days when rats are refed after starvation for 5 days.