Exchange of phosphatidylcholine between rabbit erythrocytes and plasma in vivo

Phosphatidylcholine exchange between rabbit erythrocytes and plasma was studied in vivo. The erythrocyte phosphatidylcholine was labeled by exchange in vivo with [32P] phosphatidylcholine and in vitro by acylation with [3H] 16:0 and [14C] 18:2. The erythrocytes were then injected into rabbits and the loss of labeled phosphatidylcholine from the cells by exchange was followed. The rate constants for the exchange of [32P]-, [3H] 16:0-, and [14C] 18:2-phosphatidylcholine were .013 +/- .0010, .0093 +/- .0014 and .0074 +/- .0013 h-1, and the exchange rates of the labels relative to that of [32P] were 1.0, 0.71 +/- .16, and 0.56 +/- .14, respectively. These results confirm our earlier in vitro findings and represent the first in vivo demonstration of the dependency of the exchange rate of erythrocyte phosphatdylcholines on their metabolic prehistory.