Other Peptide Receptors

Burt, David R.

doi:10.1007/978-94-010-9547-1_5

Cited by 2 publications

(1 citation statement)

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“…Although commercially available tritiated thyrotropin releasing hormone ([3H]TRH) has proved adequate as a lig and for TRH receptors in the anterior pituitary gland [8,17,28] and cell lines derived from it [10][11][12][13][14][15][16], attempts to study TRH receptors in the central nervous system (CNS) by binding of [3H]TRH [3][4][5][6] have been hampered by high blanks. These arise both from the low concentration of ap parent TRH receptors in the CNS and from the presence of interfering low affinity but saturable binding sites.…”

mentioning

confidence: 99%

Preparation of 3H-[3-Me-His2]TRH as an Improved Ligand for TRH Receptors

Taylor¹,

Burt²

1981

Neuroendocrinology

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[³H]-[3-methyl-His²]thyrotropin releasing hormone ([³H]MeTRH) binds to sites in the sheep anterior pituitary gland which appear to be the same as those occupied by [³H]TRH and which can therefore be identified as TRH receptors. In competition experiments performed in parallel, both ligands gave the same number of binding sites, 15 pmol/g wet weight, and showed the same pharmacology for 19 TRH analogs ranging over more than 5 orders of magnitude in potency. The apparent dissociation constant of binding of [³H]MeTRH was about 3.5 nM compared to 29 nM for [³H]TRH. Kinetic experiments with [³H]MeTRH yielded a rate constant for association of 1.4 × 10⁷M^–1 min^–1 and rate constants for the bi-phasic dissociation of 5 × 10^–2 min^–1 (fast phase) and 7 × 10^–3 min^–1 (slow phase). Detailed methods are described for preparation of [³H]MeTRH by reduction of the dehydroproline precursor and its purification by ion exchange and antibody affinity chromatography. The major advantage of the new ligand is that its higher affinity of binding gives relatively less nonspecific binding than is obtained with [³H]TRH, particularly in central nervous tissue.