Effects of melatonin on blood cells

Daily subcutaneous injection of melatonin in a dose of 200 ug [0.5 ml] for seven days in one group of rats and for twenty-one days in another group produced an increase in the total number of WBCs, neutrophils, lymphocytes, eosinophils and basophils. These changes were marked in the twenty-one days treated group of rats. In seven days treated group, melatonin produced an increase in RBCs count and PCV% associated with a decrease in MCH and MCHC. In twenty-one days treated group, melatonin decreased PCV, Hb, MCV, MCH and MCHC. These findings suggested an immunostimulatory role for melatonin