The effect of 3, 5, or 9 days of M-CSF administration on carbon particle clearance in SW mice. Mice were injected with 4 mg/kg/d M-CSF, administered in two daily IP injections, 8 hours apart, starting on day 1. Mice received the final injection of M-CSF on the morning of the indicated day, approximately 2 hours before the injection of the carbon particles on day 3, 5, or 9. The mean absolute absorbance of lysed blood at 620 nm at 1 minute was 1.091 (n = 12) for the control animals, 0.717 (n = 6) for mice treated with 3 days, 0.566 (n = 6) for mice treated with 5 days, and 0.637 (n = 6) for mice treated with 9 days of M-CSF. These values were designated as 100%, and subsequent results were calculated as a percentage of the 1-minute values. The means ± 1 SE are shown. The T1/2 values obtained after 3 days (3.7 ± 0.4 minutes), 5 days (2.8 ± 0.2 minutes), and 9 days (3.9 ± 0.5 minutes) of M-CSF treatment were significantly shorter (faster clearance) than the T1/2 in the control mice (12.0 ± 0.7 minutes) (P < .0001), but were not significantly different from each other.
