Histological study of the effect of potassium bromate on the thyroid gland of adult male albino rats and the protective role of vitamin C supplementation

ABSTRACT

Thirty adult male albino rats were used in this study aiming to study the effect of chronic oral administration of potassium bromate on the structure of the thyroid gland and to study the possible protective role of the concomitant supplementation of vitamin C. The animals were divided equally into three groups [10 animals each]; a control group and two experimental ones. The animals of the first experimental group were subdivided equally into 2 halves. The animals of the first half were given a daily oral dose of potassium bromate 30 mg/kg body weight for successive 2 months. While the animals of the other half were given the same daily oral dose of potassium bromate for successive 6 months. The animals of the second experimental group were also subdivided equally into 2 halves. These animals were given a daily intraperitoneal injection of 20 mg/kg body weight of vitamin C for 2 and 6 months respectively simultaneous with a daily oral dose of potassium bromate as in the first experimental group. At the time of sacrifice, all the animals of each group were anaesthetized with ether inhalation and their thyroid glands were dissected out carefully and processed for light and electron microscope examinations. Light microscope observations of the thyroid glands of the potassium bromate treated rats for 2 months revealed alterations of many thyroid follicles. Their follicular cells became squamous with deeply stained nuclei. Ultrastructurally, the follicular cells contained irregular heterochromatic nuclei. Their cytoplasm contained dilated rough endoplasmic reticulum and swollen mitochondria. Mast cells were seen in the connective tissue between the affected follicles. Light microscope examination of the thyroid glands of the rats treated with potassium bromate for 6 months showed loss of the architectures of the glands. The follicular cells appeared with deeply stained nuclei and marked cytoplasmic vacuolations. Ultrastructrually, the follicular cells contained dilated and fragmented rough endoplasmic reticulum. Their nuclei showed irregular outlines and much clumps of heterochromatin. While light and electron microscope examinations of the thyroid glands of the animals treated with vitamin C concomitant with potassium bromate revealed preservation of the architectures of the glands. Most of their follicles appeared with few colloid. The follicular cells contained well developed rough endoplasmic reticulum with some dilated cisternae, numerous mitochondria with few swollen ones and cytoplasmic vacuolations. In conclusion, the results of this study revealed that chronic oral administration of potassium bromate led to structural changes in the thyroid gland which were duration dependant. Vitamin C supplementation with potassium bromate showed a moderate protection against these alterations