Male Wistar rats (n = 24) aged four months and weighing 150–200 g were procured from National Centre for Laboratory Animal Supplies (NCLAS), Hyderabad, India. All the animals were maintained under standard laboratory conditions in a light–dark cycle (12:12 h) with the temperature between 12 C and 25 C. The rats were divided into four experimental groups (control, 20 ppm, 60 ppm and 100 ppm) with six animals in each group, respectively. Drinking water containing 20 ppm, 60 ppm and 100 ppm NaF (Sigma, St. Louis, MO) was administered to three groups for 90 days, whereas the rats in the control group were fed with tap water containing permissible limit of fluoride (0.8 ppm) for the same period. The animals had free access to the laboratory chow and water throughout the duration of the study and sacrificed on 90th day of the experiment by cervical dislocation. The study protocol was approved by Animal Ethics committee of Department of Zoology, Osmania University, Hyderabad, India (CPCSEA No: 383/01/a/ CPCSE).