Specific high affinity binding sites for somatostatin-28 on pancreatic beta-cells: differences with brain somatostatin receptors.

摘要: Saturable and high affinity binding sites have been obtained for an iodinated somatostatin-28 (SS-28) analog, [Leu8,D-Trp22125I-pyr25] SS-28, in a membrane preparation from hamster insulinoma, mainly composed of pancreatic β-cells. Specific is maximal after 1 hour incubation at 22 C represents 65% the total binding. KD [Leu8,D-Trp22,Tyr25] SS-28 0.25 nM with number corresponding to 68 fmol/mg protein. The (lnM) more than 5 times lower that SS-14. analogs, such as [D-Trp22] analogs which selectively inhibit insulin releass vivo (Des-Asn5[D-Trp8,D-Ser13] SS-14 Des-Asn 19[D-Trp22D-ser27] SS-28), are most potent compounds this assay. C-terminal replacement Lcysteine by D-cysteine reduces apparent SS analogs. Unrelated peptides inactive analog Des-Trp8-SS-14 no insulinoma sites. There differences between those monitored under simi...