The relation of oxygen supply to water movement and to urea formation in surviving liver tissue.

Liver slices have been immersed during periods up to 4 hours at 38 degrees C. in Krebs-Ringer solution with bicarbonate buffer and exposed to varied oxygen supply in the presence of carbon dioxide equal to that of venous blood. Water movement, urea, and amino acid formation by the liver tissue have been measured. Water contents of surviving liver tissue diminishes with increased oxygen supply, but during life the maximum limit of oxygen is determined by that brought by the arterial blood and has an approximate partial pressure of 100 mm. Hg. Urea formation by liver slices is increased by increased oxygen supply but does not occur with anoxia. Osmotic pressure within liver cells is maintained in part by amino acids and related substances, and in part by electrolytes. Diminished osmotic pressure and loss of water is explainable by oxidation of nitrogenous substances with formation of urea which leaves the cells. These changes within a limited range of variation are adjustable to functional needs.