Bone Abstracts

There is a growing body of evidence indicating the important role of the neonatal steroid milieu in programming sexually dimorphic pattern in various physiological systems. We tested the hypothesis that abnormal exposure to steroid hormones within a critical developmental period elicits permanent changes on tooth eruption, enamel mineralization, and leptin and corticosterone concentrations in adulthood. Newborn Wistar rats were divided into four groups, two male groups and two female groups. Male pups were cryoanesthetized and submitted to castration or sham-operation procedures within 24 h after birth. Female pups received a s.c. dose of testosterone propionate (100 μg) or vehicle. Lower incisor eruption was determined between the 4th and the 10th postnatal days, and the eruption rate was measured between the 40th and the 60th days of age. After extraction, performed 60 days, the upper incisors rights were used to obtain data related enamel mineralization, assessed by microhardness testing. The plasma leptin and corticosterone secretions were analyzed by RIA. The results of this study demonstrate that the androgenized female had delay on teeth eruption when compared with control females. The sham-castrated males had higher growth rate of normofuncional tooth eruption than the other groups. The enamel microhardness in both prismatic and aprismatic areas were higher in control females than all the other groups studied. Regarding the profile of hormone secretion, plasma concentrations of leptin in castratred males in the neonatal period were lower when compared to other groups, and plasma concentrations of corticosterone were not statistically different between groups evaluated. In conclusion, the study show that neonatal steroids manipulation causes well-defined oral disturbances in adulthood in rats, and suggests the importance of the neonatal sex steroid milieu for normal sexual dimorphic pattern on tooth eruption, enamel mineralization, as well as on hormonal secretion.