Increase in housing temperature can alleviate decrease in white blood cell counts after energy restriction in C57BL/6...

White blood cell (WBC) counts decrease after energy restriction (ER) in both rodents and humans. ER reduces cellular proliferation rates in various organs of rodents. Increases in housing temperatures can cancel this inhibitory effect of ER. We investigated whether a high housing temperature can alleviate decreases in WBC counts after ER, since peripheral WBC counts at basal levels are considered to represent cellular proliferation rates in the bone marrow. C57BL/6 female mice were allocated to three groups: the control (397 kJ/week), the ER (176 kJ/week) and the ER housed-in-incubator group (ERI: 134 kJ/week). The former two groups were housed at 21-23 degrees C and the third group was housed at 30 degrees C. At 4 and 13 months of age, WBC counts were significantly lower in ER or ERI mice than in control mice. WBC counts, however, were significantly higher in ERI mice (194%) than in ER mice at 13 months of age. A high housing temperature was proved to antagonize the effect of ER on WBC counts, as it antagonizes suppressive effects of ER on cellular proliferation rates in various organs.