Endocrinology, Vol 110, 1049-1051, Copyright © 1982 by Endocrine Society

ARTICLES

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

JC Reubi, J Rivier, M Perrin, M Brown and W Vale

Saturable and high affinity binding sites have been obtained for an iodinated somatostatin-28 (SS-28) analog, [Leu8,D-Trp22,125I-Tyr25] SS- 28, in a membrane preparation from hamster insulinoma, mainly composed of pancreatic beta-cells. Specific binding is maximal after 1 hour incubation at 22C and represents 65% of the total binding. KD for [Leu8,D-Trp22,Tyr25] SS-28 is 0.25 nM with the number of sites corresponding to 68 fmol/mg protein. The KD for SS-28 (1nM) is more than 5 times lower than that for SS-14. SS-28 analogs, such as [D- Trp22] SS-28 and analogs which selectively inhibit insulin release in vivo (Des-Asn5[D-Trp8,D-Ser13] SS-14 and Des-Asn19[D-Trp22,D-Ser27] SS- 28), are the most potent compounds in this assay. C-terminal replacement of L-cysteine by D-cysteine reduces the apparent affinity of SS analogs. Unrelated peptides and the inactive analog Des-Trp8-SS- 14 have no affinity for insulinoma binding sites. There are differences between the insulinoma SS binding sites and those monitored under similar conditions from rat cerebral cortex. In cerebral cortex, SS-14 and SS-28 have similar affinity for the binding sites, and the insulin selective analogs are less potent than SS-14. It is concluded that pancreatic beta-cells, as well as brain, possess high affinity binding sites for SS, but that they differ in some of their pharmacological properties.

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				V. Tran, M. Beal, and J. Martin Two types of somatostatin receptors differentiated by cyclic somatostatin analogs Science, April 26, 1985; 228(4698): 492 - 495. [Abstract] [PDF]