MOLECULAR PHARMACOLOGY, 45:410-416 Rat Somatostatin Receptor Type 1 Couples to G Proteins and Inhibition of Cyclic AMP Accumulation

The pharmacology, signal transduction, and coupling to G pro-teins of the rat somatostatin (SRIF) receptor (SSTR)l have been characterized in transfected Chinese hamster ovary (CHO) (Ki strain) cells. The expressed receptor exhibited saturable, high affinity binding of several radioiodinated SAlE analogues. Three different radioligands were used to determine the pharmacolog-ical properties of this SSTR subtype. [1251-Tyr11]SRIF-14 (1251-S-1 4), [Leu8,D-Trp,125I-Tyr5]SRIF-28 (125l-S-28), and cyclo(D-Trp-Lys-Abu-Phe-MeAla-1251-Tyr)(1251-peptide C) displayed the follow-ing rank order of affinity (Kd) for the SSTR1 subtype: 1251-S-l 4 125I-S-28> 1251-peptide C. Competition of 1251-S-l 4 with S-i 4, 5-28, or peptide C displayed the same rank order of potency. Chemical cross-linking of specifically bound 125l-S-28 to mem-branes from CHO cells expressing the receptor indicated that the molecular weight of the SSTR1 expressed in CHO cells is---70,000, suggesting that it is heavily glycosylated. Previou