Quantitative changes in the lysosomal vacuolar system of rat hepatocytes during short-term starvation. A morphometric analysis with special reference to macro- and microautophagy.
Ultrastructural morphometric analysis was used to study time-dependent variations in macro- and microautophagy in rat hepatocytes. Except during periods of short-term starvation for up to 24 h, animals were kept under standardized conditions of food intake. In hepatocytes of meal-fed rats the volume fraction of macroautophagic vacuoles is significantly higher at 23:00 h, i.e., immediately before food intake, compared to 11:00 h, i.e., 12 h following feeding. During fasting, macroautophagy drops to a low level. Microautophagic vacuoles in hepatocytes of meal-fed rats, sacrificed at 11:00 or 23:00 h respectively, do not show any significant quantitative differences. However, during 12 h of starvation, the volume fraction of microautophagic vacuoles rises significantly, whereas the numerical density remains constant. Subsequently, during the second 12-h period of fasting, the volume fraction of microautophagic vacuoles remains unchanged, but the numerical density increases. Over a period of 24 h of starvation the volume fraction of the total lysosomal system does not change significantly, whereas the numerical density rises. The time-dependent changes of the macroautophagic vacuolar system correlate with the circadian, food-related variations in the protein content of individual hepatocytes from meal-fed animals. The increase in volume fraction and thereafter in number of microautophagic vacuoles, as observed during starvation, coincides with a large decrease in protein content of individual hepatocytes.
D000818:Animals; D001343:Autophagy; D008099:Liver / Q000378:metabolism / Q000648:ultrastructure*; D008247:Lysosomes / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D009940:Organoids / Q000378:metabolism*; D010587:Phagocytosis; D051381:Rats; D011919:Rats, Inbred Strains; D013217:Starvation / Q000378:metabolism / Q000473:pathology*; D013997:Time Factors; D014617:Vacuoles / Q000378:metabolism* / Q000648:ultrastructure