EXPRESSION OF THE PROLIFERATING CELL NUCLEAR ANTIGEN (PCNA) IN THE RAT-THYROID GLAND AFTER EXPOSURE TO BROMIDE

Analysis of expression of the proliferating cell nuclear antigen (PCNA ) was used to determine the presumed hyperplastic character of morphol ogical changes in the rat thyroid evoked by bromide administration. Ma le rats fed by a standard diet with determined iodine and bromine cont ent were given potassium bromide. Control animals received no bromide. Experimental animals were given 10, 50 or 100 mg Br- per 11 drinking water for 16 and 66 days, or 100, 200, 400 mg Br-/l drinking water for 133 days. The thyroids of treated animals showed activation of growth of the epithelial follicular component as well as diffuse and focal m icrofollicular rearrangement of the parenchyma with higher follicular cells accompanied by a decrease of the amount of colloid even at low b romine concentrations (10-100 mg Br-/l drinking water). Using the PCNA -LI index (PCNA-positive nuclei 100/total number of follicular cell nu clei in the section), immunohistochemical analysis of PCNA in the nucl ei of the follicular cells was carried out in parrafin sections. The i ndex was significantly higher in bromide exposed animals (P < 0.01) an d correlated well with the histological changes, with bromide concentr ation and with a increased mitotic activity of the follicular cells. P CNA analysis showed that morphological changes resembling a parenchyma tic goitre reflect a microfollicular rearrangement of the thyroid of r ats exposed to bromide and have the character of hyperplasia owing to the increased mitotic activity of the follicular epithelium.