The effect of in vitro and in vivo cellular aging on the active calcium transport in human inside-out red cell membrane vesicles.

Modelling of the in vivo and in vitro aging processes in the human red cell has stressed the following features of the active calcium uptake by inside-out vesicles: 1) it is higher in the outdated, in vitro aged, than in the fresh red cell (p less than 0.0005), and in the densest, in vivo aged fraction than in the lightest, young fraction (p = 0.08); 2) it increases following stimulation by excess calmodulin to values that are not significantly different; 3) it decreases to the same value in the absence of endogenous calmodulin and inhibitor, with and without exogenous calmodulin; 4) it is the target of a non-competitive inhibition, that is stronger in the fresh than in the outdated red cell. We conclude that the aging process does not involve neither membrane Ca-ATPase nor calmodulin, but rather the interaction of the calcium pump with the inhibitor of Ca-ATPase.