40 female and 20 male Sprague–Dawley rats (180–220 g) were obtained from the Laboratory Animal Center of Hubei Provincial Center for Disease Control and Prevention. Standardized pellet diet and drinking water were available ad libitum. All rats were kept in a controlled environment at (23–27)°C, 55–60% humidity, conforming to a 12 h light/dark cycle. The experimental protocols were approved by the Ethics Review Committee for Animal Research at Archives of Toxicology (2019) 93:709–726 711 1 3 Huazhong University of Science and Technology and were implemented exactly as specified. After 1-week acclimation, rats of the same sex were ranked by weight and divided randomly into the following four groups: one control group (tap water, containing less than 1.0 mg/L F−), and three NaF-treated groups (NaF was administered orally via drinking water; dosages were set as 10, 50, and 100 mg/L NaF (corresponding to 4.52, 22.6 and 45.2 mg/L F−, respectively) ). After 2 months of NaF exposure, rats in each group were chosen randomly for mating according to the ratio of male-to-female as 1:2. Then the pregnant female rats were kept in separate cages throughout gestation and subsequent weaning of pups, during which the corresponding NaF exposure still continued. The day of birth was considered as postnatal day 0 (PND 0). On PND 21, the offsprings were re-caged to five single sex pups in one cage and exposed to the same NaF concentration as the adult rats did until PND 60 (2 months of age).