Studies on the mechanical fragility of erythrocytes. I. Normal values for infants and children.

REINHOLD, B.M., M.R.C.P., D.C.H. AND 1)AvID YI-YUNG HSIA, M.D. I ORDER to obtains a better ttnderstanding of tise factors causitsg destruction of human erythrocytes its vivo, a number of methods have beets devised to test their susceptil)ihty to destructions by various forces applied in vitro. By manipulation of temperature, pH, osmotic equilih)rium and by the addition of hemolysitis, ithas beets possil)le coissisteistly to (letect abnormalities in certaits disease states. Although the use of mechaisical shakitsg its the (Iestructiots of erythrocytes was first suggested by Meltzer’ its 1884, it ss’as Rous2 who stated that “resistance to hypotonic solutions is in iso real setise ats itsdex to fragility of red 1)lOOd cells. A clinical investigatiots of this fragility as determitsed by shakitig experiments might tsot be svit-hout importaisce.” Shets3 demonstrated that the fragility of erythrocytes subjected to the measured mechatsical trauma of rolling glass beads stays withits well defined limits in normal persons and shows sigtsificant increase in conditions such as cotsgetiital and acquired hemolytic anemias. Young46 has felt that the process of mechatsical fragility simulates most closely the physiologic conditions in the blood stream. Both Young and Shen3 have found that in getseral mechatiical fragility is tsearly always increased when osmotic fragility is itscreased, but in some imsstamsces mechanical fragility may he increased whets osmotic fragility is tiormal or actually decreased. By the use of cells tagged w’ith radioactive irons, Stewart and his co-workers7 have showts that young eryt-hrocytes its (logs have a mechanical fragility les.s thats thatof the general red cell population, while the osmotic fragility is relatively increased. They also showed that with agitig of the red cell, the mechanical fragility finally exceeds that of the gemseral red cell population. They poitit outthat although the “wear atsd tear” imposed ots the erythrocyte in the laboratory test is more severe thais thatw’hich may occur its vivo because of the isecessity for testitsg over a short period of time, the life spats of the cell may 1)e partly limited by factors w’hich itscrease its mechatsical fragility its vivo.