Osmometric behavior of normal and abnormal human erythrocytes.

By GEORGE M. GUEST, M.D. V ARIOUS investigators have postulated two main principles which seem to govern the swelling and hemolysis of red blood cells suspended in hypotonic salt solutions: namely, the cells imbibe water according to the laws of osmosis, and their maximum swelling is limited by an inelastic surface membrane. According to this concept, hemolysis occurs when the erythrocytes in hypotonic solutions attain a critical volume at which the cells rupture and allow hemoglobin to escape. Studies of the physico-chemical mechanisms involved in the processes of osmotic swelling and hemolysis of erythrocytes have involved a great deal of controversy, especially over the question of whether the mammalian red cell behaves as a per.. fect osmometer,’ ‘ adapting itself to changes in osmotic pressure of surrounding fluids by the transfer of water a’one (Ponder Is). Evidence assembled by Ponder’9 from many sources indicates that: the erythrocytes of various species sometimes do behave as perfect osmometers, but at other times and under varying conditions they behave as decidedly imperfect osmometers. The reasons for this variable behavior are still obscure. Methods devised for the measurement of the osmotic fragility of red cells have had clinical applications especially valuable in the diagnosis of congenital hemolytic jaundice and in the differential diagnosis of other types of hemolytic disease. The first development of such a method is generally ascribed to Hamburger1#{176} who in 1883 devised a test that involved the notation of “beginning” hemolysis and ‘complete” or total hemolysis, or the points of minimal and maximal resistance of red cells suspended in a series of solutions of diminishing concentrations of sodium chloride. Jolly’6 states that even earlier, in i88o, Chanel2 described a method for measuring red cell fragility in hypotonic salt solutions and applied it in clinical studies. It is of interest to note that Chanel’s was a quantitative test, in contrast to the essentially qualitative test of Hamburger. According to Jolly, Chanel made suspensions of blood cells in a series of salt solutions of diminishing concentrations and after a given time determined the number of cells destroyed by counting the intact cells. By this method he demonstrated diminished osmotic resistance of erythrocytes in certain anemias and increased resistance in certain types of jaundice. Whitby and Hynes24 independently developed approximately the same procedure in 1935. Several refinements of Hamburger’s procedure have been suggested to disclose minor differences in cell fragility that characterize certain pathologic types of red cells (Wintrobe25 ); but the noteworthy advances in methodology are mainly confined to quantitative measurements of hemolysis. Estimations of the degree of hemolysis at each point in the hemolytic series have