[Molecular biology, pharmacology and signal transduction of 5 cloned human somatostatin receptors].

Somatostatin is a hormone with inhibitory properties, which is expressed in several tissues including the gastrointestinal tract. Actually, somatostatin and somatostatin-analogues are used for the treatment of neuroendocrine tumors and esophageal varices. Somatostatin acts via specific receptors. So far, five somatostatin receptor subtypes have been isolated and cloned. They are characterized by a high degree of sequence homology. The different receptor subtypes recognize the naturally occurring and the pharmaceutically developed ligands with different affinities. The receptor subtypes are expressed in a tissue-specific manner and in different tissues they couple to different signal-transduction pathways. The somatostatin receptors are also expressed in several malignant tissues. But the expression pattern varies from tumor to tumor. The availability of the receptors and their cDNAs allows the characterization of somatostatin's molecular action in greater detail. The design of even more potent somatostatin anlogues seems possible as well as the development of new therapeutical strategies.