Effect of Fasting on Protein Release by Liver Slices

¹ From the Department of Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem, Israel

The release of total nitrogen from rat tissue slices into an artificial medium was investigated under different experimental conditions. Protein was found to be the main nitrogeneous component released. Liver slices from fed rats release much less total nitrogen into the medium than those from fasted rats. This fasting effect is specific for liver tissue. A protein-free diet lowers total nitrogen release from liver slices, whereas a protein-rich diet raises it. Refeeding either the stock diet or a protein-free diet for one night after a 5-day fast, lowers total nitrogen release to the level of that in fed animals. However, this is not the case after refeeding a low-ration diet. The fasting effect does not exist in rats fed a fat-rich, carbohydrate-free diet; it is lower than usual in rats fed a protein-rich, carbohydrate-free diet. The administration of glucose by stomach tube to fasted rats lowers total nitrogen release to normal fed levels in 2 hours.