Objective To investigate the morphological alternations of pituitary luteinizing hormone ( LH ) cells and the serum concentrations of levonorgestrel ( LNG ) - treated rats. Methods The pituitary LH cells were identified by immunohistochemistry and computer images analysis system. The serum concentrations of LH were measured by IMMULITE automated analyzer. Results In short - term treated group, the shape of LH cells became round ( P < 0. 01 ) and the gray level ( P < 0. 05 ) of LH cells increased, while the number and mean area of LH cells had no significant difference as compared with that in control group( P > 0. 05 ). In long - term treated group, the number and mean areas of LH cells decreased ( P <0. 01 ) and the shape became irregular. The serum concentrations of LH were significantly lower in treated group than those of control group in both terms ( P <0. 01 ). After ceasing treatment, these changed features recovered to normal gradually ( P < 0. 01 ). Conclusion LNG caused changes of morphology of LH cells and concentrations of LH in serum, but these changes can return to normal afterceasing treatment. The decrease of the pituitary response to GnRH caused by short - term treatment of LNG play an important role on antiovulation, while long - term effects perhaps also involve central mechanisms such as influence on hypothalamus, making synthesis and release of GnRH decrease.%目的 分析左旋18-甲基炔诺酮(levonorgestrel,LNG)对大鼠垂体黄体生成素(luteinizing hormone,LH)细胞形态和血清浓度的影响.方法 应用免疫组织化学方法结合计算机图像分析,观察应用LNG后大鼠垂体LH细胞的变化,同时应用自动化学发光免疫分析仪测定血清LH浓度.结果 短期实验组大鼠LH细胞形状变圆(P＜0.05),灰度加深(P＜0.05),而细胞数量和平均面积无明显改变(P＞0.05);长期实验组大鼠LH细胞形状不规则,细胞数量和平均面积减少(P＜0.01);短期和长期实验组大鼠血清LH浓度均下降(P＜0.01);停药后LH细胞数量,平均面积及血清LH浓度逐步恢复正常(P＜0.01).结论 应用LNG可以引起大鼠垂体LH细胞形态及血清LH浓度的改变,但这一过程是可恢复的.短期应用主要作用部位在垂体前叶.长期应用同时抑制了下丘脑GnRH的合成与分泌,从而抑制排卵.
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