Bone Marrow Hypoplasia Induced by Administration of Estradiol Benzoate in Male Beagle Dogs

Abstract

Six male beagle dogs were administered estradiol benzoate (E₂) for 30 days at a dose of 0.1 mg/kg every day or 0.3 mg/kg every 3rd day and changes in hematology, bone marrow cells and the blood coagulation were investigated. Bleeding tendencies with severe thrombocytopenia occurred 15 or 18 days after the first E₂ injection. Three of 6 dogs died of the intra-thoracic hemorrhage on days 21, 33 and 45 respectively. White blood cells first increased to 4-10×10⁴/mm³ on days 15-21, then decreased thereafter. Red blood cells first decreased and then slowly increased after days 21-27. Platelets increased transiently soon after the E₂ administration, but then decreased rapidly and were below 3000/mm³ on day 15. After day 24, platelets again increased. By the bone marrow examinations, myeloid cells increased and erythroid cells decreased considerably on days 15-18. After day 24, myeloid cells decreased and erythroid cells increased and the total number of marrow cells decreased at the end of the experiment. There were no abnormal findings in the coagulation examinations in all the dogs.