Thyrotropin-Releasing Hormone (TRH), Free Acid (TRH-OH)

Thyrotropin-Releasing Hormone (TRH), Free Acid (TRH-OH) is a physiological metabolite of Thyrotropin-Releasing Hormone.

TRH degradation products have been shown to be associated with a number of endocrine- and central nervous system-related biological functions. TRH (pGlu-His-Pro-NH2) can be enzymatically degraded in plasma and brain tissue to yield TRH-OH. TRH and hGHRH stimulate the release of [3H]GH into the culture medium to 435 and 464%, respectively, when compared to the control, but TRH-OH has no effect[1]. TRH-OH, produced after cleavage of the C-terminal amide group by a specific proline endopeptidase, is one of the most stable derivatives of TRH and is found at high levels in numerous brain regions. TRH-OH inhibits Na+ channel activity in mammalian septal neurons. In about 60% of the cells tested, TRH-OH at concentrations between 0.01 and 2.5 μM produces a dose-dependent reversible attenuation of Na+ currents. With 2 μM TRH-OH, peak Na+ current amplitude is reduced by 20-50%[2].

[1]. Kagabu Y, et al. Effects of thyrotropin-releasing hormone and its metabolites, Cyclo(His-Pro) and TRH-OH, on growth hormone and prolactin synthesis in primary cultured pituitary cells of the common carp, Cyprinus carpio. Gen Comp Endocrinol. 1998 Sep;111(3):395-403. [2]. López-Barneo J, et al. Thyrotropin-releasing-hormone (TRH) and its physiological metabolite TRH-OH inhibit Na+ channel activity in mammalian septal neurons. Proc Natl Acad Sci U S A. 1990 Oct;87(20):8150-4.