New specific radioligand for one subpopulation of brain somatostatin receptors.
Cyclic octapeptide analogues of somatostatin (SS) like SMS 201-995 [H-(D) Phe-Cys-Phe-(D) Trp-Lys-Thr-Cys-Thr(ol)] or its Tyr3-derivative 204-090, displaced [125I-Tyr11]-SS 100% from pancreatic membranes but only 62-75% from brain membranes; the remaining sites were displaced by SS. These data indicate that some mini-somatostatins bind to a subpopulation of SS receptors in rat brain. The iodinated Tyr3-derivative (125I-204-090) can be considered a selective radioligand for one rat brain SS receptor subpopulation: It shows saturable and high affinity binding (KD = 0.29 nM; Bmax = 350 fmoles/mg protein) to rat cortex. The pharmacological properties of 125I-204-090 binding sites are similar to those of [125I-Tyr11]-SS sites. Distribution of these sites correspond to SS receptor-rich areas such as cortex, hippocampus, striatum, pituitary, pancreatic beta-cell. SS as well as SMS 201-995 bind to these sites with high affinity. The stability and high specific vs non-specific binding ratio makes 204-090 a radioligand of choice to measure this SS receptor subpopulation in CNS but also the SS receptors in pituitary and pancreas.
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D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D015282:Octreotide / Q000031:analogs & derivatives; D010179:Pancreas / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D011956:Receptors, Cell Surface / Q000032:analysis*; D017481:Receptors, Somatostatin; D013004:Somatostatin / Q000031:analogs & derivatives / Q000378:metabolism
D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D017481:Receptors, Somatostatin; C045210:3-Tyr-octreotide; D013004:Somatostatin; C032367:somatostatin, Tyr(11)-; D015282:Octreotide