The expression of PCNA was proved in some organs of human fetuses aged from 10 to 25 weeks of the intrauterine development. The distinct expression of PCNA was demonstrated in the nuclei of the myoblasts of the ventricles and atria of the fetal heart. The high expression of PCNA was found in the nuclei of the epithelial cells of the fetal bronchial tree, surrounding mesenchyme and in the nuclei of the endothelial cells of the primitive vessels. The highest expression of PCNA was demonstrated in the nuclei of the cells of the "neogene zone" of the primitive kidney. The distinct expression of PCNA exhibited the nuclei of the cells of the surface zone of the primitive adrenal cortex and the cells of the primitive islets of the adrenal medulla. The expression of PCNA was demonstrated in the primitive hepatocytes, endothelial cells of the liver sinusoids and epithelial cells of the bile ducts and in the epithelial cells of the intestinal anlage.

Institut für Histologie und Embryologie Medizinische Fakultät der Palacký Universität Olomouc Tschechische Republik