Thyrotropin-releasing hormone receptor expression in thyroid follicular cells: a new paracrine role of C-cells?
M. De Miguel1, J.M. Fernández-Santos1, J.C. Utrilla1, A. Carrillo-Vico2, J. Borrero2, E. Conde1, J.M. Guerrero2 and I. Martín-Lacave1
1Departament of Normal and Pathological Histology, and 2Departament of Biochemistry and Molecular Biology, Faculty of Medicine, University of Seville, Seville, Spain
Offprint requests to: Inés Martín-Lacave, Dpto. Citología e Histología Normal y Patológica, Facultad de Medicina, Universidad de Sevilla, Avda. Sánchez-Pizjuán s/n, 41009 Sevilla, Spain. e-mail: ilacave@us.es
Summary. Thyrotropin-releasing hormone (TRH) synthesized in the hypothalamus has the capability of inducing the release of thyroid-stimulating hormone (TSH) from the anterior pituitary, which in turn stimulates the production of thyroid hormones in the thyroid gland. Immunoreactivity for TRH and TRH-like peptides has been found in some tissues outside the nervous system, including thyroid. It has been demonstrated that thyroid C-cells express authentic TRH, affecting thyroid hormone secretion by follicular cells. Therefore, C-cells could have a paracrine role in thyroid homeostasis. If this hypothesis is true, follicular cells should express TRH receptors (TRH-Rs) for the paracrine modulation carried out by C-cells. In order to elucidate whether or not C-cell TRH production could act over follicular cells modulating thyroid function, we studied TRH-Rs expression in PC C13 follicular cells from rat thyroid, by means of immunofluorescence technique and RT-PCR analysis. We also investigated the possibility that C-cells present TRH-Rs for the autocrine control of its own TRH production. Our results showed consistent expression for both receptors, TRH-R1 and TRH-R2, in 6-23 C-cells, and only for TRH-R2 in PC C13 follicular cells. Our data provide new evidence for a novel intrathyroidal regulatory pathway of thyroid hormone secretion via paracrine/autocrine TRH signaling. Histol Histopathol 20, 713-718 (2005)
Key words: TRH-R, Rat thyroid, C-cells, Follicular cells
DOI: 10.14670/HH-20.713