Thyrotropin-releasing hormone receptor expression in thyroid follicular cells: a new paracrine role of C-cells?
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.
De Miguel
M
M
Departament of Normal and Pathological Histology, Faculty of Medicine, University of Seville, Avda. Sánchez-Pizjuán s/n, 41009 Seville, Spain.
Fernández-Santos
J M
JM
Utrilla
J C
JC
Carrillo-Vico
A
A
Borrero
J
J
Conde
E
E
Guerrero
J M
JM
Martín-Lacave
I
I
D000818:Animals; D002460:Cell Line; D005455:Fluorescent Antibody Technique / Q000379:methods; D015870:Gene Expression; D019899:Paracrine Communication / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D018025:Receptors, Thyrotropin-Releasing Hormone / Q000032:analysis / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism*
D012333:RNA, Messenger; D018025:Receptors, Thyrotropin-Releasing Hormone