Modification of Carbohydrate Determinants of the Eyeball Structural Components on the Background of Experimental Hyperthyroidism According to the Lectin Histochemistry Data

Objective: Endocrine ophthalmopathy occurs in patients with autoimmune thyroiditis and in people without a clinically expressed pathology of the thyroid gland. At present, many questions of thyropathies’ pathogenesis remain insufficiently  tudied. It is known, that TSH receptors are localized on connective tissue fibroblasts, muscle elements and adipose tissue of the orbit. However, the effect of hyperthyroidism on morphology and cytotopography of the lectins receptors of the eyeball structural components has been less studied.

Aim: To investigate the morphological peculiarities and cytotopography of lectin receptors of the rat eyeball structural components under conditions of experimental hyperthyroidism.

Methods: Experiments were performed on 30 Wistar rats – males with weight 180-240g, (10 control and 20 experimental). Exogenous hyperthyroidism was induced by daily administration with food the drug L-thyroxine (Berlin-Chemie) at a dose of 150 mg/kg body mass within 20 days. Samples of thyroid glands and eyeballs were fixed in Bouin’s solution and embedded in paraffin. Sections 5-7 μm thick were stained by hematoxylin and eosin in order to study the general morphology of the  nvestigated objects. Carbohydrate determinants have been studied by means of lectin-peroxidase technique using the panel of 6 lectins with different carbohydrate specificity (LABA (αL-Fuc), PNA (βDGal), WGA (NАcDGlc NА NА), HPA (αNАcDGal), SNA (NeuNAc(α2-6)DGal) та CNFA (GalNAcβ1). Lectin receptors visualization was conducted in 3’3-diaminobenzidine  tetrahydrochloride system in Н2О2 presence.

Results: It has been shown that under the influence of experimental hyperthyroidism general morphological and morphometric changes were observed, which were manifested by the intensity of apoptotic processes in the anterior epithelium of the cornea, local desquamation of the surface layers of the anterior epithelium, and

its detachment from the basement membrane. In the retina – by apoptotic processes in separate ganglion neurons and reduction in the thickness of the retina, modification of carbohydrate determinants in structural components of different layers of the retina and high specificity of lectin binding with corneal keratocytes both in control and experimental animals.

Соnclusion: Under the L-thyroxine influence, both morphological changes and changes in the carbohydrate profile of the eyeball structural components were observed.