TIMING OF RECOMBINANT HUMAN GRANULOCYTE-COLONY-STIMULATING FACTOR ADMINISTRATION ON NEUTROPENIA INDUCED BY CYCLOPHOSPHAMIDE IN NORMAL MICE

The effects of altering the timing of recombinant human granulocyte co lony-stimulating factor (rhG-CSF) administration on neutropenia induce d by cyclophosphamide (CPA) were studied experimentally in a mouse mod el. Experimental mice were divided into three groups: (a) treatment wi th rhG-CSF after CPA administration (post-treatment group); (b) treatm ent with rhG-CSF both before and after CPA administration (pre- and po st-treatment group); and (c) treatment with saline after CPA administr ation (control group). The results were as follows. Mice receiving rhG -CSF on the 2 days preceding CPA treatment, in which progenitor cell c ounts outside the S-phase when CPA was administered were the lowest of all the groups, showed accelerated neutrophil recovery but decreased neutrophil nadirs compared with the control group despite rhG-CSF trea tment. The pre- and post-treatment group, consisting of mice who recei ved rhG-CSF treatment on days -4 and -3 before CPA treatment, and in w hich progenitor cell counts when CPA was administered were increased t o greater levels than in the other groups, showed remarkably accelerat ed neutrophil recovery and the greatest increase in the neutrophil nad irs of all the groups. These results suggested that the kinetics of pr ogenitor cell populations when chemotherapeutic agents were administer ed seemed to play an important role in neutropenia after chemotherapy, and that not only peripheral neutrophil cell and total progenitor cel l counts but also progenitor cell kinetics should be taken into consid eration when administering rhG-CSF treatment against the effects of ch emotherapy.