[Circadian variations of the mortality of mice due to cadmium sulfate]

If circadian variations in tolerance to drugs have been often demonstrated, such observations about heavy metals are still very scarce. The present study proposes to determine if circadian variations occur in the tolerance of Mice to single lethal dose of cadmium sulphate. 400 female mice, kept in cages on a 8.00-20.00 L/D cycle, received IP a single cadmium sulphate injection at different doses (2.5, 3, 3.5 and 4 mg/kg) at different hours in the day (8.00, 14.00, 20.00 and 2.00 hrs.). Death number was determined each day during 10 consecutive days. The mortality percentage is a function of the time of the cadmium administration, varying between 3.3 and 21.7% for 2.5 mg/kg, between 16.7 and 43.3% for 3 mg/kg, between 33.3 and 71.7% for 3.5 mg/kg and between 73.3 and 96.7% for 4 mg/kg. The metal is the most toxic at 20.00 hr (mean: 58.3%) and the least at 2.00 hr. (mean: 33.7%). A circadian susceptibility to cadmium sulphate in Mice thus clearly appears, as has been recently described with mercury and platinum.