Morphological and biochemical changes in the Harderian gland of hypothyroid rats

Abstract

SUMMARYThe 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.

Chromosome 19 open reading frame 80 is upregulated by thyroid hormone and modulates autophagy and lipid metabolism

“…27 Notably, autophagic vacuoles are reduced in the Harderian gland of hypothyroid rats. 22 In our experiments, LAMP2, an important factor for autolysosome fusion, 28 was induced by T 3 and associated with C19orf80, consistent with the theory that T 3 is involved in vacuolization and degradation. Accordingly, we postulated that C19orf80 functions in lysosome activity, focusing on T 3 -induced autophagic flux.…”

“…22 Accordingly, we examined whether T 3 alters the autophagic response, thus enhancing the accumulation of acidic organelles. After 48 h stimulation with T 3 , phosphatidylethanolamine-conjugated microtubule-associated protein 1 light chain 3 (LC3-II) was increased in conjunction with downregulation of SQSTM1 (also known as p62), a cargo receptor that is degraded by the autophagic process (Fig.…”

Tear staining in finisher pigs and its relation to age, growth, sex and potential pen level stressors

“…However, pigs with a higher ADG may experience stressors such a metabolic stress or higher competition at the feeder due to a higher motivation to feed. The growth of pigs is not only controlled by growth hormones but also by the thyroid hormones (Cabello and Wrutniak, 1989), and it has been shown in the rat and the hamster that changes in the level of the thyroid hormones may change TS as well (Hoffman et al, 1990, Baccari et al, 2004, Monteforte et al, 2008. Thus, the positive relation between ADG and TS may simply be found due to a hormonal difference between pigs with different growth rates.…”

Compromised epidermal barrier stimulates Harderian gland activity and hypertrophy in ACBP−/− mice

“…Furthermore, similar to Harderian glands from ACBP Ϫ / Ϫ mice, glands from K14-ACBP ؊ / ؊ these enzymes and/or increased substrate fl ux. Choline and T3 have been shown to stimulate secretion from the Harderian gland in rats (36)(37)(38)(39)(40). However, neither plasma levels of T3 nor glandular choline levels were affected by ACBP depletion at 28 days of age or in adult mice ( Fig.…”