Characterisation of human recombinant somatostatin receptors. 1. Radioligand binding studies

Abstract

Human somatostatin receptor subtypes 1-5 (sst1-5) were characterised using the agonist radioligands [125I]LTT-SRIF28, [125I][Tyr10]CST14, [125I]CGP 23996 and [125I][Tyr3]octreotide in stably transfected Chinese hamster lung fibroblast cells (CCL39 cells). The radioligands used labelled saturable and high-affinity populations of sites in each instance; at sst1-4 receptors maximum binding (B(max)) was roughly equivalent. By contrast, at sst5 receptors B(max) determined with [125I]CGP 23996 and [125I][Tyr3]octreotide was significantly lower (two-and eightfold) compared with [125I]LTT-SRIF28 and [125I] [Tyr10]CST14. Experiments were performed with the stable GTP-analogue guanylylimidodiphosphate..