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First published online February 1, 2008
Journal of Experimental Biology 211, 606-612 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.015115
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Morphological and biochemical changes in the Harderian gland of hypothyroid rats

Rossella Monteforte1, Alessandra Santillo1, Antonia Lanni1, Salvatore D'Aniello2 and Gabriella Chieffi Baccari1,*

1 Dipartimento di Scienze della Vita, Seconda Università degli Studi di Napoli, via Vivaldi, 43, 81100-Caserta, Italy
2 Department de Genetica, Facultat de Biologia, Universitat de Barcelona, Spain

* Author for correspondence (e-mail: gabriella.chieffi{at}unina2.it)

Accepted 11 December 2007

The secretory activity of the Harderian gland (HG) is influenced by both exogenous (such as light and temperature) and endogenous (such as prolactin, thyroid hormones and steroid hormones) factors, which vary among species. In the present study, the effects of hypothyroidism on the rat HG were examined at morphological and biochemical levels. The decrease in cytoplasmic lipoproteic vacuoles and the increase in mucosubstance secretion in the acinar lumina were the most notable histological effects elicited by hypothyroidism. The release of all granules with nuclei and cellular debris suggested the occurrence of holocrine secretion. Electron microscopy revealed in the glandular cells of hypothyroid rat an increased condensation of chromatin in the nuclei, mitochondria with decreased cristae and vacuolisation, decreased glycogen granules, autophagic vacuoles, and lipofuscins in the cytoplasm. TUNEL reaction indicated DNA fragmentation in hypothyroid HG, indicative of an underlying apoptotic process. Translocation of cytochrome c from mitochondria to cytosol strongly supported this hypothesis. In conclusion, these findings indicate that thyroid hormones play a pivotal role in preserving the structural integrity of the rat HG and, hence, its secretory activity.

Key words: Harderian gland, ultrastructure, hormone action, hypothyroidism






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