The effects of Ca(2+) ions and the nutritional state of the animals on the distribution of soluble protein between the medium, cytoplasmic and particulate fractions after incubation of rat-liver slices have been studied. 2. The Ca(2+)ions decreased the leakage of cytoplasmic protein into the medium and increased the loss of protein from the particles; the effects were more marked with livers from starved animals and animals fed on a low-carbohydrate diet. 3. The results obtained for protein were confirmed by measurements of the changes in distribution of compartment-specific enzymes, and these indicated that both the cytoplasmic and particulate fractions contributed to the protein found in the medium. 4. EDTA decreased the loss of protein and enzymes from both the cytoplasmic and particulate fractions; this effect was independent of the Ca(2+) ion concentration. 5. The inclusion of pyruvate, succinate or citrate in the medium had no marked effects on the leakage of protein.
