Diurnal variations of serum GM-CSF levels

We aimed to investigate the daily variations of serum granulocyte-macrophag e colony-stimulating factor (GM-CSF) levels and to correlate them with peri pheral blood cells counts, Venous blood samples from eleven healthy volunte ers were taken four times a day, being at 08:00, 14:00, 20:00 and 02:00h an d serum GM-CSF levels measured by ELISA, We could not find a significant ov erall difference among GM-CSF levels at four different times of the day usi ng the Friedman test, On the other hand, serum GM-CSB levels at night (20:0 0h) were found to be significantly increased when compared to the morning l evels (08:00h) using the Wilcoxon test (P=0,022), The levels of lymphocytes and white blood cells (WBCs) at 20:00h mere also higher than the morning l evels (08:00h) as expected, While there was a strong relationship between t he morning levels of GM-CSF (08:00h) and all measurements of peripheral blo od cells during the day, the levels of GM-CSF measured at 02:00, 14:00 and 20:00h were found to be significantly correlated with only the WBC levels, It was concluded that there may be a significant difference between morning and night levels of GM-CSF and morning levels of GM-CSF may be more import ant in the regulation of WBC counts during the day, These variations warran t further studies about diurnal rhythms of haematopoiesis chronotherapy wit h CSFs. (C) 2000 Academic Press.