Liver lysosomes in protein-starved rats.

I . The feeding of a protein-free diet to adult rats trained to consume their whole day’s food in z h changed the characteristics of hepatic lysosomes immediately upon the onset of protein deficiency combined with calorie deficiency. 2. The nature of the alterations in the characteristics of liver lysosomes were deduced from the faster release of enzymes, swelling of membranes and a change in the sedimenting properties. Purified lysosomes from pooled livers from a group of rats fed on a protein-free diet for only a day, showed marked differences when compared with lysosomes from normal rats. When lysosomes were suspended in sucrose solutions of two different molar concentrations, the release of acid phosphatase occurred at a faster rate in liver lysosomes of protein-starved rats than in those of normal ones. The light-scattering characteristics of the suspensions suggested the presence of swollen lysosomes in livers of rats fed on a protein-free diet and normal lysosomes in the livers of control rats. 3. rn homogenate of liver from rats fed on a protein-free diet for 11 days the levels of cathepsin and acid ribonuclease showed a fiveto six-fold increase in the free specific activities when compared with those of controls. 4. The role of lysosomes is discussed with reference to the accumulation of hydrolytic endproducts and liver autolysis during protein starvation.