The effect of aspartame on the pituitary thyroid axis of adult male albino rat and the possible protective effect of Pimpinella anisum oil: histological and immunohistochemical study

Background: Aspartame is a synthetic sweetener. Its metabolites can be toxic to many organs such as liver and kidney. Pimpinella anisum (P. anisum) has been used for different purposes as an antioxidant, hepatoprotective, and anti-inflammatory agent. Aim: The present work was carried out to study the histological changes in the pituitary thyroid axis of adult male albino rats after aspartame treatment and the possible role of P. anisum in minimizing these changes. Materials and methods: Twenty-five adult male Albino rats were used. They were divided into three groups: group I was the control group, group II received 250 mg/kg/day aspartame once daily for 2 months, and group III received prophylactic P. anisum oil 0.5 ml/kg/day once daily, followed by aspartame after 2 h for 2 months. At the end of the experiment, the rats were sacrificed. The thyroid and pituitary gland tissue samples were processed for light microscopic and electron examination. Also, an immunohistochemical study was carried out for the detection of thyrotrophs. Results: Light microscopic examination of aspartame-treated animal showed loss of architecture of the thyroid gland. Many follicles were small in size and others had disrupted wall and detached cells in their lumens. Some thyrocyte had pyknotic nuclei and deeply stained vacuolated cytoplasm. There was a highly significant increase in the number of positive immunostained thyroid-stimulating hormone cells. Most cells in pars distalis were hypertrophied with eccentric nuclei and a large negative Golgi image. The thyrotrophs and somatotrophs had dilated cisternae of rough endoplasmic reticulum, destroyed mitochondria, and few secretory granules. Some cells with secretory granules of both somatotrophs and thyrotrophs were frequently observed. The administration of P. anisum induced improvements in the degenerative changes of this axis. Conclusion: From this study, it could be concluded that prolonged consumption of aspartame induced disturbance in the pituitary thyroid axis. The use of P. anisum decreased the toxic effect of aspartame.