[Effect of methotrexate-induced neutropenia on the periodontal lesion in rats]

The purpose of the present study was to investigate histologically the effect of methotrexate-induced neutropenia on the periodontal lesion in rats. In the experiment I, seventy rats were used. A suturing nylon thread was inserted between the maxillary 1st and 2nd molars for 3 weeks to produce a slight inflammation of the gingival tissue. Then, the animals were divided equally into the control and experimental groups. The animals of the experimental group were injected with 7.5 mg/kg of methotrexate once a day for 3 days. The animals of the control group were injected with saline in the same manner. The animals were killed at 1, 3, 5, 7, 9, 11 and 13 days after the last injection. During the sacrifice, peripheral blood was taken from all animals. White blood cells and neutrophils were counted and the periodontal tissues were examined by light microscopy. In the experiment II, ten rats were used. The animals were inserted with a suturing nylon thread as in the experiment I and then they were divided into the control and experimental groups. the animals of the experimental group were injected with 7.5 mg/kg of methotrexate once a day for 3 days, whereas the animals of the control group were injected with saline in the same manner. At 7 days after the last injection, peripheral blood was taken from all animals and then the animals were killed. Neutrophils were isolated from peripheral blood and the chemotaxis of these neutrophils were examined with the 48-well micro chemotaxis chamber. The periodontal tissues were examined by light microscopy. In the experiment I, the white blood cell count (WBC) and neutrophil count (NC) of the control animals did not show any changes. However, WBC and NC of the experimental animals decreased at 5 and 7 days. The control animals did not show any changes except for a slight inflammatory cell infiltration of the gingival connective tissue. The experimental animals exhibited remarkable resorption of the alveolar bone and inflammatory cell infiltration of the periodontal ligament at 5, 7 and 9 days. In the experiment II, WBC and NC of the experimental animals decreased compared with those of the control animals. The periodontal tissues of the control animals showed the changes similar to those of the control animals at 7 days in the experiment I. The periodontal tissues of the experiment animals also showed the changes similar to those of the experimental animals at 7 days in the experiment I.(ABSTRACT TRUNCATED AT 400 WORDS)