DISTRIBUTION OF PROTHYMOSIN-ALPHA IN RAT AND HUMAN ADRENAL-CORTEX

Background: Prothymosin alpha (ProT) is a polypeptide widely distribut ed in the organism and expressed by cell types with a high proliferati ve capacity. The aim of the current work was to investigate if ProT wa s localized in the progenitor compartment of the adrenal cortex which, following the cell migration theory, corresponds to the zona glomerul osa. Methods: We studied by immunohistochemical and in situ hybridizat ion methods the distribution of ProT in rat and human adrenal cortex. Immunohistochemical techniques for the study of the proliferating cell nuclear antigen (PCNA) and incorporation of 5-bromo-2'-deoxyuridin du ring DNA synthesis were also done. Immunoelectron microscopic procedur es were performed to determine the exact subcellular localization of P roT. Results: ProT was found in the zona glomerulosa cells, but not in the cells of the remaining cortical layers (zonae fasciculata and ret icularis). Glomerulosa cells showed immunostaining for ProT only in th e nuclei, excluding the nucleoli. Variability in immunostaining intens ity was found between different glomerulosa cells. In situ hybridizati on of ProT mRNA confirmed that ProT synthesis in adrenal cortex occurs only in the zona glomerulosa. The results obtained for proliferating cell nuclear antigen and incorporation of 5-bromo-2'-deoxyuridin confi rmed that adrenocortical proliferation occurs in the zona glomerulosa. Ultrastructural immunocytochemistry showed labelling for ProT over th e euchromatin, but not on the heterochromatin aggregations nor the nuc leoli. Conclusions: The results presented here: 1) support the migrati on theory for the adrenocortical cell renewal, 2) demonstrate that Pro T is present in the nuclei of proliferating cells (being associated wi th euchromatin), and 3) suggest that the study of ProT expression woul d be useful in distinguishing cycling from resting cells. (C) 1994 Wil ey-Liss, Inc.