Maintenance of cation gradients in cold-stored erythrocytes of guinea pig and ground squirrel: improvement by amiloride.

Red blood cells of ground squirrel, a hibernator, gain Na at one-third the rate of guinea pig red blood cells when stored in saline medium at 5 degrees C for several days. This result correlates with the known slower loss of K during storage in ground squirrel cells. In ground squirrel cells Na gain is balanced by K loss, so that there is no net gain of solute; in guinea pig cells the total cation content rises progressively. Amiloride, a drug which inhibits Na entry, retards Na uptake in cells of both species. Surprisingly, amiloride also slowed K loss and, in guinea pig red cells, the decline of ATP content. In guinea pig cells amiloride reduced the gain of total cation by half. The results substantiate the difference in cold sensitivity of ion regulation of red blood cells of these two species and demonstrate the possible usefulness of amiloride-type drugs in nonfreezing preservation of red blood cells.