Expression of thyrotropin-releasing hormone receptors in rat testis and their role in isolated Leydig cells.
Thyrotropin-releasing hormone (TRH) was initially discovered as a neuropeptide synthesized in the hypothalamus. Receptors for this hormone include TRH-receptor-1 (TRH-R1) and -2 (TRH-R2). Previous studies have shown that TRH-R1 and TRH-R2 are localized exclusively in adult Leydig cells (ALCs). We have investigated TRH-R1 and TRH-R2 expression in the testes of postnatal 8-, 14-, 21- 35-, 60-, and 90-day-old rats and in ethane dimethane sulfonate (EDS)-treated adult rats by using Western blotting, immunohistochemistry, and immunofluorescence. The effects of TRH on testosterone secretion of primary cultured ALCs from 90-day-old rats and DNA synthesis in Leydig cells from 21-day-old rats have also been examined. Western blotting and immunohistochemistry demonstrated that TRH-R1 and TRH-R2 were expressed in fetal Leydig cells (in 8-day-old rats) and in all stages of adult-type Leydig cells during development. Immunofluorescence double-staining revealed that newly regenerated Leydig cells in post-EDS 21-day rats expressed TRH-R1 and TRH-R2 on their first reappearance. Incubation with various doses of TRH affected testosterone secretion of primary cultured ALCs. Low concentrations of TRH (0.001, 0.01, and 0.1 ng/ml) inhibited basal and human chorionic gonadotrophin (hCG)-stimulated testosterone secretion of isolated ALCs, whereas relatively high doses of TRH (1 and 10 ng/ml) increased hCG-stimulated testosterone secretion. As detected by a 5-bromo-2'-deoxyuridine incorporation test, the DNA synthesis of Leydig cells from 21-day-old rats was promoted by low TRH concentrations. Thus, we have clarified the effect of TRH on testicular function: TRH might regulate the development of Leydig cells before maturation and the secretion of testosterone after maturation.
Zhao
Yong
Y
Department of Histology and Embryology, Fourth Military Medical University, Xi'an, 710032, People's Republic of China.
Hou
Wu-Gang
WG
Zhu
Hua-Ping
HP
Zhao
Jie
J
Wang
Rui-An
RA
Xu
Ruo-Jun
RJ
Zhang
Yuan-Qiang
YQ
D000818:Animals; D006728:Hormones / Q000494:pharmacology; D007985:Leydig Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008698:Mesylates / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000187:drug effects / Q000378:metabolism*; D018025:Receptors, Thyrotropin-Releasing Hormone / Q000187:drug effects / Q000378:metabolism*; D013737:Testis / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D013739:Testosterone / Q000096:biosynthesis*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D006728:Hormones; D008698:Mesylates; C114581:Mlnr protein, rat; D043562:Receptors, G-Protein-Coupled; D018025:Receptors, Thyrotropin-Releasing Hormone; C535055:TRH-receptor-1, rat; D013739:Testosterone; D013973:Thyrotropin-Releasing Hormone; C002994:ethylene dimethanesulfonate