[Morphological changes in the lower incisor of suckling rats induced by large dose of aspirin]

Large doses of aspirin (200 mg/kg or 400 mg/kg, s.c) caused marked hypocalcemia in suckling rats, two hours after administration. The hypocalcemic effect was more evident in two week old rats than in one week old ones. Although the mechanism of aspirin-induced hypocalcemia is not clear at this moment, the drug can be a useful tool for inducing experimental hypocalcemia in suckling rats, besides hormonal and/or nutritional controls. In this report, large doses of aspirin were administrated to new born rats, once at one week after birth, or twice at one and two weeks after birth. The morphological changes of the lower incisor were examined using computer programs which have been developed for the analysis of plane curves such as the traces of the side view of the incisor. Aspirin administration shortened the length of the lower incisor and its labial trace. The width of the incisor, especially in the middle, was also diminished by aspirin administration. These observations suggest that the drug not only induced hypocalcemia in suckling rats but also to some extent suppressed the activity of odontoblasts which produce the dentin of the incisor. Analysis of curvature variance, calculated with the labial trace of the lower incisor, also suggested that large doses of aspirin had two effects. It suppressed mineralization of the teeth through its hypocalcemic effect, and it inhibited synthesis of the collagenous matrix. The computer programs applied in this study have proved useful in determining and analyzing morphological changes of bio-materials which are difficult to measure directly.