[Within-day and day-to-day variations of serum M-CSF levels in healthy volunteers]

We have investigated on within-day and day-to-day variations of serum M-CSF levels in healthy volunteers (ranges of age: 20-21 years old). M-CSF levels in serum were measured using enzyme-linked immunosorbent assay (ELISA). Serum M-CSF levels in early morning were 1.31 +/- 0.30 ng/ml (mean +/- SD, n = 10) in male volunteers, 1.50 +/- 0.13 ng/ml (n = 10) in female volunteers. No significant difference was observed between male and female volunteers in serum M-CSF levels. No significant within-day variations in serum M-CSF levels were also observed. Serum M-CSF levels in period of thirteen days in each individual person were almost constant (n = 5). The inverse correlation was observed between M-CSF levels and number of neutrophils. The correlation, however, was not observed between M-CSF levels and number of monocytes. The present results suggest that there are mechanisms in vivo which maintain serum M-CSF in a constant level in each individual person.