PROLIFERATING CELL NUCLEAR ANTIGEN (PCNA) DETECTION OF CELLULAR PROLIFERATION IN HYPOTHYROID AND HYPERTHYROID RAT HEARTS

Immunocytochemical techniques examining the expression of cell prolife ration-related markers such as proliferating cell nuclear antigen (PCN A), may be employed to provide visual and quantitative evidence of cel l proliferation. The efficacy of this method in frozen samples was tes ted on sections of 2-day-old rat heart. Mouse monoclonal anti-PCNA and goat anti-mouse IgG(2a) peroxidase-conjugated antibodies were applied to tissue cross-sections. PCNA positive (PCNA+) cells were evident in these sections as intensely stained, dark brown nuclei, This method w as then applied to the hearts of four groups of adult rats (1) 1 month hyperthyroid, (2) 1 month hypothyroid, (3) 6 days hyperthyroid follow ing 1 month hypothyroidism, or (4) euthyroid, in order to assess the a bility of identifying and quantifying PCNA+ cell types (myocyte, endot helial, or remaining, ''other'' cells), Serial cross-sections were pre pared, half of the sections processed using the PCNA technique, while corresponding sections were stained with hematoxylin and eosin, Identi fication of PCNA+ cell types was made by comparison of PCNA with H&E s ections, PCNA labeling indices for a given cell type were expressed as the proportion of PCNA+ nuclei per 1000 nuclei. No PCNA+ myocyte nucl ei were observed in any of the adult hearts. Only hypothyroid/hyperthy roid demonstrated significantly higher PCNA labeling of endothelial an d ''other'' nuclei compared to euthyroid. This finding agrees with pre vious morphometric data which suggested capillary growth in these hear ts. Results demonstrate that quantitation of PCNA expression on frozen heart tissue is possible, and can be used to provide direct, discerni ble evidence for cell proliferation. (C) 1995 Academic Press Limited