Chronobiology and Chronopharmacology of the Haemopoietic System

Circadian rhythms in surface molecules of rat blood lymphocytes

“…The acrophase of the leukocyte number occurred around the beginning of this period, as already described for Lewis and SpragueDawley rats (12,14) and similar to what has been reported previously in mice (25). Daily changes in blood leukocyte counts have been attributed to a rhythmic cell distribution between the circulating and the marginal compartments, between blood and other tissues, and to a rhythmic influx of new cells (36). Although all leukocyte populations contribute to the circadian rhythm, our results showed that lymphocytes were the main contributor to that oscillation.…”

“…In humans, total white blood cell counts peak in the evening/night. Among them, neutrophil and NK cell numbers reach a maximum in the afternoon, monocytes and lymphocytes at night, T cells at midnight, and B cells in the early morning (33,36). In nocturnal animals like rat and mouse, the number of total white blood cells, lymphocytes, and Th and B cells peaks during the resting period (12,14,25,29).…”

Circadian variation of granulocyte colony stimulating factor levels in man

“…Lasky et al (1983) found that circulating uncommitted pluripotential precursors (CFU‐GEMM) formed more colonies late in the day. Other studies have shown a circadian variation in human bone marrow DNA synthesis which peaks at noon (Smaaland, 1997). It is therefore possible that these proliferative changes are mediated by the changes in G‐CSF levels.…”

“…It is therefore possible that these proliferative changes are mediated by the changes in G‐CSF levels. This may help explain why bone marrow toxicity induced by chemotherapeutic agents may markedly differ depending on the time of administration (Smaaland, 1997), and is important because glucocorticoids are frequently part of a chemotherapeutic regimen, and may alter toxicity (Smaaland, 1997), conceivably by virtue of G‐CSF release. Finally, a recent study in mice suggests that the pharmacokinetics and pharmacodynamics of G‐CSF may underlie considerable diurnal variations (Ohdo et al , 1998).…”

Circadian variations of bone marrow engraftability

“…The existence of circadian rhythms within the hematopoietic system was recognized a long time ago. Differentiated cell types and different progenitor classes, including day‐8 CFU‐S, CFU‐GM, BFU‐E, CFU‐E, and CFU‐GEMM have been shown to exhibit distinct circadian rhythms and to show seasonal variations (Smaaland, 1997; Wood et al, 1998; Kolaczkowska et al, 2001). This was demonstrated by measurement of DNA synthesis, mitotic index, or clonogenic tests.…”