| 60-day rat water |
Subchronic (30-90 days) |
A dose of NaF (500 ppm daily in drinking water) that produced growth retardation in a previous study (Harrison et al. 1984) was chosen for the present study. Four groups of animals received NaF (LR, Qualigens Fine Chemicals, Mumbai, India; 500 ppm with drinking water) or CaCO3 (GR Sarabhai M Chemicals, India; 50 mg/kg), both together or tap water daily for 60 days...Animals receiving tap water for 60 days served as untreated control… In another study, animals received 500 ppm of NaF with drinking water daily for 60 days, and the next 60 days NaF was withdrawn from the drinking water. Food and water intake were measured daily during these (withdrawal) 60 days. The tests described below were carried out 24 hr after the 60th day of withdrawal of NaF treatment. The respective control animals received balanced diet and tap water for 120 days and tests were carried out 24 hr later as in the withdrawal group; Colony-bred 3–4 month old female Wistar rats weighing 130–150 g were used. Female rats were used in this study because in a previous study in this laboratory, mortality occurred in male and not in female animals during 60 day oral treatment with toxic doses of NaF (Paul et al. 1998). Eight animals were chosen randomly for each test and control group. Animals were caged singly, since food and water intake were recorded in both test and control groups. The animals were maintained at room temperature (22–26°) with normal 12 hr light/dark cycle and fed ad libitum, a balanced commercially available pelleted rat feed containing 1% of calcium (Gold mohur, M/s.Hindustan Lever Ltd., Mumbai, India) and NaF mixed tap water containing 40 ppm of calcium. The background concentration of fluoride in drinking water was 0.2 ppm. Guidelines defined by the Ministry of Social Justice Empowerment, Government of India (Singh 1998) was followed in this study |