WBCs, including neutrophils, monocytes, and eosinophils, produce reactive oxygen species ROS and nitric oxide species NOS, which are chemically reactive molecules 40 tadalafil cialis It is also possible that the peptide has an effect on red blood cell production, given the report of Ucn2 gene expression in bone marrow, 37 although this is unlikely to have produced the precipitous hematocrit declines and post treatment increases observed in this study because bone marrow effects are usually seen over days weeks and months