Protective effect of nimustine hydrochloride against radiation-induced pulmonary injury in mice

Female C3H/HeN mice were irradiated in the thorax at a dose ranging from 10 to 25 Gy with or without ACNU (nimustine hydrochloride) treatment in order to determine whether the chemotherapeutic agent would lead to an enhancement of radiation-induced lung damage. ACNU given intravenously at 15 mg/kg immediately prior to irradiation reduced the mortality of mice irradiated with a low dose; mortality with either radiation alone or radiation plus ACNU was 4/10 (40%) or 0/10 (0%) at 13.1 Gy, and 9/10 (90%) or 6/10 (60%) at 15 Gy, respectively. The presence of ACNU during thoracic irradiation also prolonged the survival time of mice approximately 2-fold over that of animals given radiation alone. Histological examination of mice sacrificed 80 days after treatments revealed that the combination of drug and irradiation produced no radiation pneumonitis, which was predominant in mice given radiation alone. It is unexpectedly concluded that ACNU may have a protective effect against radiation-induced lung injury.