EXPRESSION AND COUPLING OF SOMATOSTATIN RECEPTORS IN RAT ADRENAL (PC12) AND PITUITARY (GC) CELL-LINES

Somatostatin (somatotropin release-inhibiting factor, SRIF) interacts with G-protein coupled receptors (sst) designated sst1 through sst5. I n PC12 and GC cells, SRIF binding sites were identified and mRNA recep tor expression was evaluated. SRIF binding sites were expressed at a m uch lower density in PC12 (K-d = 21.2 +/- 3.9 nM; B-max = 31 +/- 8 fmo l/mg protein) than in GC cells (K-d = 6.4 +/- 1.6 nM; B-max = 643 +/- 29 fmol/mg protein), sst3 receptor mRNA (81% of the total) was mainly expressed in PC12 cells, while sst1/2 receptor mRNAs were mostly expre ssed in GC cells (64 and 29%, respectively). In PC12 cells, adenylyl c yclase (AC) activity was unaffected by SRIF-14 (binding all SRIF recep tors), octreotide (specific for sst2/3/5 receptors), BIM 23056 (bindin g sst3/5 receptors) or CH275 (specific for sst1 receptors), 1 mu M eac h. In GC cells, SRIF-14 or octreotide, but not the two other peptides, significantly inhibited AC activity. (C) 1998 Elsevier Science Irelan d Ltd. All rights reserved