The action of melatonin on the blood dynamics of pregnant rats and on the histogenesis of the spleen and thymus of offspring

We investigated the influence of melatonin on the hemogram of pregnant rats and puppies, and on the histogenesis and morphology of the spleen and thymus of puppies. Melatonin was administered at a dose 0.5mg/kg body weight, dissolved in 0.1mL of ethanol and diluted in 0.3mL of saline. For hematocrit analysis, total erythrocyte count and total and differential leukocyte count, blood samples were collected on the 7th, 14th and 21st days of pregnancy and the offspring at 10 days of birth. Histological sections of spleen and thymus of the offspring were used for histochemistry and morphometry. The absence of melatonin promoted changes in blood count only in the final third of gestation, without interfering with the hemogram of the puppies, and induced morphological and morphometric changes in the thymus and spleen in the first days of life of the puppies. It was concluded that maternal melatonin is important for the modulation of the blood count in pregnant rats and the normal development of the spleen and thymus of the offspring.