XXXX pharmacokinetics in age-fractionated erythrocytes.

@entity1 @entity1499 @entity492 @entity1500
Age fractionation of erythrocytes is useful for further studies of the pharmacokinetics of @entity1499 ( @entity1500 ) in red blood cells. We separated erythrocytes from five blood donors and four @entity1 at different time points after @entity1500 infusions, using discontinuous Percoll gradients consisting of four solutions with a difference of 3% in density among them. The procedure yielded five distinct fractions of erythrocytes of increasing mean cell age as judged by declining reticulocyte enrichment and erythrocyte @entity492 aminotransferase activity among the five fractions. @entity1500 concentrations of the erythrocytes were measured at different times in connection with five 24-h @entity1500 infusions (0.7-4 g/m2) on 14 occasions. Two days after completion of @entity1500 infusion, no @entity1500 was detected in the youngest erythrocyte population in two @entity1 . Seven days after the infusion, the highest @entity1500 concentrations were found in the youngest red blood cells. Ten to fourteen days following the @entity1500 treatment, considerably lower @entity1500 concentrations were found in the young red blood cells, and the @entity1500 -containing erythrocytes seemed to have moved down the gradient. Just before the next @entity1500 infusion (after 28 days) no @entity1500 could be detected in the young erythrocytes. The @entity1500 concentrations at that time were highest in the oldest erythrocyte fractions. This study shows more directly that @entity1500 is incorporated in the red cell precursors of the bone marrow. The pharmacokinetics demonstrated correspond to a maturation time of the erythroblasts of about 7 days.
