HISTOLOGY AND HISTOPATHOLOGY

Cellular and Molecular Biology

 

Ghrelin localization in the medulla of rat and human adrenal gland and in pheochromocytomas

K. Raghay1, T. García-Caballero1, S. Bravo2, C.V. Alvárez2, R. González2, C. Diéguez2, A. Beiras1, M. Fraga3 and R. Gallego1

1Department of Morphological Sciences, 2Department of Physiology, 3Department of Pathology, Faculty of Medicine-University Clinical Hospital, University of Santiago de Compostela, Santiago de Compostela, Spain.

Offprint requests to: Prof. Tomás García-Caballero, Department of Morphological Sciences, Faculty of Medicine, University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain. email: cm-tgc@usc.es


Summary. Objective: Ghrelin is predominantly produced by neuroendocrine cells of stomach and has been expressed in several normal and tumour endocrine tissues. It has been reported that the localization of ghrelin is exclusively in the cortex of human and rat adrenal gland and in adrenocortical tumours. This prompted us to analyze the expression of this peptide in medulla of human and rat adrenal glands and in human pheochromocytomas. Design and methods: Analysis of ghrelin mRNA expression in rat adrenal gland was conducted by means of semi-quantitative RT-PCR. Ghrelin localization was studied in medulla of human and rat adrenal gland by immunohistochemistry. In addition, we have carried out a double immunofluorescence with chromogranin A to determine the specific cell type expressing ghrelin immunoreactivity. Ghrelin expression was also analyzed in five cases of pheochromocytoma by immunohistochemistry. Finally, Western blotting analysis was performed with goat ghrelin antibody in the cortex and in the medulla of rat adrenal gland. Results: RT-PCR demonstrated expression of ghrelin mRNA in rat adrenal gland. We also detected ghrelin expression in virtually all rat pheochromocytes by immunohistochemistry and double immunofluorescence. Furthermore, we showed ghrelin immunoreactivity in the medulla of human adrenal gland and in pheochromocytomas. By Western blotting, we found the expression of ghrelin precursor, proghrelin and mature ghrelin in the medulla of rat adrenals. However, the cortex of rat adrenal gland only expressed ghrelin precursor. Conclusions: Our study is the first to demonstrate a medullar expression of ghrelin in human and rat adrenal gland; we also showed ghrelin expression in pheochromocytomas. Histol Histopathol 23, 57-65 (2008)

Key words: Ghrelin, Adrenal gland, Medulla, Pheochromocytoma, Immunohistochemistry

DOI: 10.14670/HH-23.57