Further Studies on the Postmortem Changes of Red Blood Cells
Postmortem changes in membrane components of red cells were investigated. The membrane components examined were sialic acid, protein subunits and lipids. Under ether anesthesia, rats were killed by stabbing in the breast to induce hemorrhage, after which blood was drawn from thorax. The observation period was limited to 18 hours after death, during which time changes in osmotic fragility and red cell shape are clearly observed. The quantity of sialic acid declined with the passage of time during this early postmortem period. The value at 18 hours was about 75 per cent of that in normal cells. The subunit patterns obtained by PAGE of membrane proteins of cells 18 hours after death were similar to those of normal red cells. In spite of the decrease in sialic acid content, PAS staining yielded no difference between normal and 18-hour-postmortem red cells, and it was thought that membrane proteins did not change markedly during this early postmortem period. It was found that changes in lipid composition happened within 3 hours of death, and fragments were observed. The decrease in free cholesterol was most remarkable, and at 18 hours after death the cholesterol level fell to about 75 per cent of that of normal red cells. The ratio of free cholesterol to total phospholipid decreased from 0.44 to 0.36. These results suggest that a significant decrease in free cholesterol in red cell membrane may hold the key as to why changes in osmotic fragility and red cell shape occur during the early postmortem period.
