Molecular sieving of red cell membranes during gradual osmotic hemolysis.

Abstract

Rat red blood corpuscles were held stationary with respect to a continuously flowing solution in either a specially constructed centrifuge or in glass filters. The concentration of the solution was gradually decreased to cause the swelling and subsequent gradual osmotic hemolysis of the cells. The passage of the intracellular molecules —potassium, adenylate kinase, and hemoglobin—across the cell membranes and into the flowing solution was determined as a function of time. Ions and molecules begin passage across the membranes in the order of increasing molecular size. The initial flow of potassium is followed by the initial flows of hemoglobin and adenylate kinase. The flow of hemoglobin has been interpreted as the flows of hemoglobin monomers, dimers, and tetramers such that the time sequence is: potassium; hemoglobin monomer; adenylate kinase/hemoglobin dimer; and finally, hemoglobin tetramer. It is concluded that the stressed cell membrane has molecular sieving properties and that the exclusion limit (effective hole size) increases as a function of time during the initial stages of gradual osmotic hemolysis. The process of gradual osmotic hemolysis is discussed in terms of molecular sieving through stress-induced effective membrane holes. It is suggested that a portion of the membrane protein might form an elastic network which would account for the gradual increase in size and apparent homogeneity of the effective holes.