[Cloning and characterization of the human thyrotropin-releasing hormone receptor: regulation of thyrotropin-releasing hormone receptor mRNA levels by thyroid hormone].

1. We successfully cloned a human thyrotropin-releasing hormone receptor (TRH-R) gene. The human TRH-R consists of 398 amino acids and is a member of the G protein-coupled receptor family. The gene has a single intron in the coding sequence. Although highly homologous to the rat and mouse TRH-Rs, the human TRH-R has several differences in the carboxyl-terminal structure. 2) We next studied the effect of thyroid status on TRH-R mRNA levels both in vivo and in vitro. TRH-R mRNA levels in hypothyroid rats were increased significantly, while no significant changes were observed in vitro. The data indicate that thyroid hormone may regulate TRH-R mRNA levels in different manners in vitro and in vivo.