Effect of recombinant canine granulocyte colony-stimulating factor on peripheral blood neutrophil counts in normal cats.

Recombinant canine granulocyte colony-stimulating factor (rcG-CSF) was administered subcutaneously at a dosage of 5 micrograms/kg/day to five healthy, young adult cats for 42 days. Mean neutrophil counts +/- standard deviation increased significantly (P < 0.001) from 10,966/microL +/- 2324 to 30,688/microL +/- 5296 within 24 hours after administration of the first dosage of rcG-CSF. Mean neutrophil counts reached 52,978/microL +/- 11,207 on day 6, representing a second significant increase (P < 0.01) over the previous 5 days. Mean neutrophil counts continued to increase, reaching 66,994/microL +/- 12,419 on day 14, then remaining within a range of 66,994 to 87,839/microL throughout the remainder of the study. The maximum mean neutrophil count was 87,839/microL +/- 8,695 on day 42. Neutrophil counts remained high until the administration of recombinant canine granulocyte colony-stimulating factor was discontinued 42 days after initiation of therapy. Once the rcG-CSF administration was discontinued, neutrophil counts returned to pretreatment values within 5 days. There were no significant changes in numbers of any of the other cell lines. There was no clinically significant toxicosis associated with the administration of rcG-CSF.