Prolonged storage of red cells with ammonium chloride and mannitol

Recently, a new preservation medium consisting of ammonium chloride added to adenine, glucose, mannitol, citrate, and potassium phosphate, was described. Unexpectedly, the predominant effect on red cell storage was an initial elevation of ATP levels, followed by remarkable maintenance of these levels at 12 to 18 weeks with acceptable 24-hour survival. The aim of the study reported here was to investigate the reasons for the advantageous effects of the different constituents. With the new preservation medium, ATP content was maintained at acceptable levels for at least 8 weeks with low spontaneous hemolysis. However, similarly high ATP levels were also maintained in the absence of ammonium chloride. Comparable results were obtained on substituting sodium for potassium salts in the new medium. When the main cation in the preservation medium was replaced by sodium, the addition of ammonium or rubidium chloride did not provide an advantage. Therefore, ammonium chloride was not essential for this medium, whereas mannitol does seem to be essential in a solution whose content of nonpermeant solutes is hypotonic.