Thyrotropin releasing hormone (TRH): apparent receptor binding in rat brain membranes.

Thyrotropin releasing hormone (TRH) binds to membranes of rat brain tissue via high- and low-affinity binding components. The high-affinity binding of TRH to brain membranes resembles binding to pituitary membranes in terms of its affinity and specificity for most peptides. In equilibrium studies, the affinity and specificity for most peptides. In equilibrium studies, the dissociation constant for high-affinity binding to brain membranes is about 50 dissociation constant for high-affinity binding to brain membranes is about 50nM, which is about the same as for aat pituitary membranes, while low-affinity binding to brain membranes has a dissociation constant of about 5 muM. Liver membranes display low-affinity binding for TRH with a dissociation constant similar to the low-affinity binding component of brain membranes. No high-affinity binding can be detected with liver membranes. Negligible saturable binding to TRH can be detected with membranes of any tissues examined other than liver, pituitary and brain...