OSMOTIC HOMEOSTASIS MAINTAINED BY MAMMALIAN LIVER, KIDNEY, AND OTHER TISSUES

Osmotic pressure maintained by liver or kidney tissue measured by its water equilibrium with solutions of sodium chloride remains unchanged from 5 minutes up to 1½ hours following removal of the tissue from the body. Then with autolytic increase of molecular concentration within the cytoplasm of cells it reaches a higher level. Osmotic pressure maintained by pancreas or submaxillary gland, as ascertained in the same way, remains unchanged during ½ hour and later increases. Liver tissue of rat, mouse, guinea pig, rabbit, and cat maintains an osmotic pressure greater than twice that of the blood, and kidney tissue maintains an osmotic pressure somewhat less than twice that of blood. Fasting throughout a period of 7 days has little influence upon osmotic pressure maintained by cells of liver or kidney. Low protein diet has been found to depress osmotic pressure of liver cells after about 4 weeks, and with degenerative changes in the parenchyma, notably fatty infiltration, this pressure has remained at a diminished level during approximately 90 days. Increase of pressure within the common bile duct and the changes following biliary obstruction are accompanied by depression of the osmotic pressure maintained by liver tissue and ligation of the ureter diminishes the osmotic pressure maintained by kidney tissue. In both instances osmotic pressure tends later to rise to its former level. The osmotic pressure maintained by liver or by kidney tissue preserves an approximately uniform level under normal conditions and may be little changed by conspicuous injury to the organ. When this osmotic homeostasis is impaired by severe injury the pressure maintained by the tissue returns to its former level with recovery from the injury.