Effect of colony-stimulating factors on number and function of circulating monocytes in normal dogs

Recombinant human granulocyte-macrophage colony-stimulating factor (rhuGM-CSF) and recombinant canine granulocyte colony-stimulating factor (rcG-CSF) were administered to normal dogs, and effect on monocyte number and function was evaluated. rhuGM-CSF, administered for 14 days, induced a 2.5-fold increase in monocyte counts on day 3. Leukocytes increased two-fold after 1 day. Counts peaked on day 11, then declined, approaching pretreatment counts by day 15. On day 7, in vivo monocyte cytostasis activity was significantly enhanced, and declined on day 14. rcG-CSF induced a 4.5-fold increase in monocyte counts on day 3. Leukocyte counts increased three-fold after 1 day. Increased counts were maintained for 69 days, at which time treatment was discontinued. There was no effect of rcG-CSF on in vivo monocyte cytostasis activity on days 7 and 14.