Effect of prolonged Orexin A and B Administration on the Pituitary-Thyroid Axis in the Rat.
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Accession number;02A0266676
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| Title;Effect of prolonged Orexin A and B Administration on the Pituitary-Thyroid Axis in the Rat. |
| Author;
MALENDOWICZ L K
(School Of Medicine, Poznan, Pol)
NOWAK K W
(Univ. School Of Agriculture, Poznan, Pol)
NERI G
(Univ. Padua, Padua, Ita)
KACZMAREK P
(Univ. School Of Agriculture, Poznan, Pol)
ZIOLKOWSKA A
(School Of Medicine, Poznan, Pol)
GINDA W J
(School Of Medicine, Poznan, Pol)
NUSSDORFER G G
(Univ. Padua, Padua, Ita)
TREJTER M
(School Of Medicine, Poznan, Pol)
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Journal Title;Biomed Res
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Journal Code:Z0236B
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ISSN:0388-6107
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VOL.22;NO.5;PAGE.229-233(2001)
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| Figure&Table&Reference;FIG.3, REF.35 |
| Pub. Country;Japan |
| Language;English |
| Abstract;Orexins(OX) A and B are hypothalamic peptides, which play a role in the central control of food intake. They act via two receptor subtypes: OX-1R which is selective for OX-A, and OX-2R which is non-selective for both OXs. RT-PCR detected the expression of OX-1R and OX-2R mRNAs in the rat hypothalamus, but not thyroid gland. Prolonged OX-A and OX-B administration (daily subcutaneous injections of 16nmol/kg OXs for 7 consecutive days) raised thyroid-gland weight. Morphometry showed that in the enlarged glands the volume of the follicle epithelium was increased, while that of colloid remained unchanged, so that epithelium/colloid ratio markedly decreased. In OX-treated rats, the plasma concentration of TSH was raised, while the blood levels of thyroid hormones were not significantly altered. Collectively, these findings indicate that systemically administered OXs enhance pituitary TSH release, mainly acting via OX-2R receptors, with the ensuing stimulation of thyroid-gland growth. The lack of sizeable changes in the level of circulating thyroid hormones can conceivably be ascribed to a inhibitory action of OXs on the secretory activity of thyroid gland, which is independent of the presence of OX receptors in follicular epithelial cells. Our study provides evidence that interrelationships occurs between OXs and hypothalamo-pituitary-thyroid axis, which is in keeping with the major role of thyroid gland in the regulation of feeding and energy expenditure. (author abst.) |
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