Cytolytic action of stored human milk on blood cells in vitro.

Stored human milk induced cytolysis on various types of blood cells depending on the storage time and temperature. When separated by centrifugation after storage for 24 h at 4 degrees C, the cream, not whey, induced cytolysis. When separated and heated for 30 min at 56 degrees C before storage, neither cream or whey induced cytolysis. When the cream was heated at 56 degrees C for 30 min and mixed with non-heat-treated whey before being storage for 24 h at 4 degrees C, it induced cytolysis. When bile salt was added to whole milk before storage, the cytolytic activity was enhanced. When eserine was added, the cytolytic activity was suppressed. Thin layer chromatography showed that stored milk, not fresh milk, contained free fatty acids which caused a similar degree of cytolysis as stored whole milk. These results indicated that the cytolysis is due to the free fatty acids which were produced from triglycerides catalyzed by the lipase in milk.